cpap te deities tn tssth Ment Mh aad ee the open level ground before us, a fox not yet fully grown standing still and watching our approach. All at once it dropped, and when we came up to the spot it was lying stretched out, with eyes closed, and apparently dead. Before passing on my com- panion, who said it was not the first time he had seen such a thing, lashed it vigorously with his whip for some moments, but without producing the slight- est effect.” Mr. Morgan in his book on the beaver gives the following instance on what he assures us is excellent authority: “A fox one night entered the hen-house of a farmer, and after destroying a large number of fowls, gorged himself to such repletion that he could not pass out through the small aperture by which he had entered. The proprietor found him in the morning sprawled out upon the floor apparently dead from surfeit; and taking him up by the legs carried him out unsuspectingly, and for some distance to the side of his house, where he dropped him upon the grass. No sooner did Reynard find himself free than he sprang to his feet and made his escape.” Dogs are frequently deceived by this ruse of. the fox and doubtless foxes have many times owed their 208 Studies in Animal Behavior lives to its aid. It has been often noticed that if one withdraws from a fox when it is feigning it may be seen to slowly open its eyes, then raise its head and carefully look around to see if its foes are at a safe distance, and finally scamper off. While in insects the instinct of feigning death is probably a simple reflex reaction to outer stimuli, it is doubtless associated in birds and especially mam- mals with a tolerably acute consciousness of the situ- ation. It involves a more or less deliberate inten- tion to profit by the deception, yet at the same time it is probably not a result of conscious reflection. The instinct is there, or else such a course of action would not occur to the animal’s mind. Were it otherwise it would be difficult to understand why the ruse is adopted only by certain species while many others, equally intelligent and for whom it would be an equally advantageous stratagem, never mani- fest it. There can be little doubt that a fox which slowly opens its eye and warily looks around is act- ing with an intelligent appreciation of his predica- ment, but it is not to be inferred that he could have reasoned out his course of action did not an innate proclivity in that direction form a part of his in- stinctive make-up. The physiological condition in what is called death-feigning is quite different in different forms. .i While there is a general relaxation of the muscu- ature in the sham death of some of the birds and - mammals, the feint in most of the lower animals The Instinct of Feigning Death 209 is characterized by a tetanic contraction of the mus- cles. The attitudes assumed by many forms, such as rolling into a ball, keeping the legs and other appendages drawn close to the body, or, in some cases, holding them straight and rigid, are such as can be maintained only at the cost of considerable muscular effort. If a Ranatra is picked up by one of its slender legs it may be held out horizontally for a considerable time without causing the leg to bend. The situation is similar to that of ‘a man seized below the knee and held out straight, face upward, without causing the knee to bend. As the legs of Ranatra are relatively exceedingly slender, the muscular tension which the insect maintains must be intense. Similar muscular rigidity is shown in the walking-stick Carausius studied by Schmidt. Specimens supported by the tip of the abdomen and the ends of the outstretched fore legs would lie straight as a stick for hours. Death feigning is markedly influenced by external conditions such as light, contact, moisture and espe- cially temperature. In experimenting with amphi- pods I have found that when the temperature is lowered the death feint persists for a considerably longer time. The same is strikingly true of the death feint of Ranatra. At temperatures higher than the normal the Severins found that the duration of the death feint in the water bugs Nepa and Belos- toma was greatly decreased. A sudden transition from a warm to a cold temperature, however, was 210 Studies in Animal Behavior found to diminish the duration of the feint in both of these species, owing possibly to the shock effect of the sudden change. The influence of light on the duration of the feint has been studied by the Severins in the forms just mentioned and by myself in the water bug Ranatra. The results agree in showing that the duration of the feint is greater in dim than in strong light, and that the feint is further shortened if a light is kept moving over the insect. The latter result, like the former, is probably due to the greater stimulation to which the feigning insect is subjected. As all these water bugs are positively phototactic, light tends to elicit an active response which antagonizes the instinct of feigning death. In a Ranatra which is induced to come out of the death feint by moving a light above it, the first signs of life manifested are orienting movements of the head which take place in perfect unison with the movements of the light. These are followed by swaying movements of the body, until finally the insect attempts to follow the light by walking or, if highly excited, by flying. It is a curious fact that while the water bugs, Nepa, Belostoma and Ranatra, feign death very readily when out of the water, they will do so much less readily when submersed in their natural ele- ment. In Ranatra repeated manipulations under the water usually fail to elicit anything but a mo- mentary and undecided response. Nepa under the same circumstances feigns for a somewhat longer The Instinct of Feigning Death ait time, and Belostoma, in exceptional cases, may feign for as much as a few minutes. Throwing any of these insects into water while they are feigning usu- ally terminates the feint at once or in a short time. The transition from air to water, even when no temperature changes are encountered, produces a marked effect on the reactions of many semi-aquatic forms. In Ranatra and certain terrestrial amphi- pods, as we have seen in a previous chapter, it pro- duces a sudden reversal of phototaxis, a change not improbably due to the influence of contact stimuli. It is not improbable that it is the influence of con- tact stimulation that terminates the death feint of aquatic bugs when they are placed in the water. Most insects and crustaceans which feign can be caused to do so repeatedly by stroking or handling them as soon as they show signs of activity. I have performed a number of experiments on amphi- pods, Ranatra, beetles and orb-weaving spiders to ascertain how long the death feint may be continued, and to determine also the lengths of successive feints. In all the forms experimented with there was found to be much variability in the behavior of different individuals, so that it was necessary to perform numerous experiments in order to arrive at trust- worthy conclusions. In general, all the forms stud- ied showed a gradual diminution in the duration of successive feints, until, often after several hours, it was no longer possible to evoke the response. Similar experiments undertaken at my request by the / 212 Studies in Animal Behavior Severins showed the same phenomenon in Nepa and Belostoma. Fabre in his studies on Scarites found an increase in the duration of the first five feints, but his observations were not sufficiently numerous to eliminate the rather large amount of variability due to unknown causes. As the feints grow shorter the attitudes of the organism become less characteristic. Amphipods and pill-bugs do not roll up so completely or keep the appendages drawn so closely to the body. Spi- ders and beetles do not assume so compact a form, and in general it may be said that the muscular sys- tem gives evidence of diminished contraction. As the death feint is usually accompanied by a tetanic contraction of the muscles one would expect to find a diminution in the duration and perfection of the response as a simple consequence of fatigue. In a similar manner the diminution of the duration of the feint that occurs under higher temperature may be due to the fact that the muscles become exhausted more quickly when the metabolism is increased by the higher temperature of the body. The experiments undertaken to ascertain what part of the nervous system is most concerned in the death feint have yielded somewhat varied results. Robertson found that in the active species of spiders Epeira and Amaurobius the sham death reaction per- sisted after the removal of the brain, and was mani- fested in a weakened form when the subesophageal ganglion and even the first thoracic were removed The Instinct of Feigning Death 213. also. Ina sluggish spider Celenia Robertson found that “The sham death posture cannot be induced without the head ganglia.” Schmidt finds that in Carausius the death feint entirely disappears after. the removal of the brain. My own experiments on Ranatra showed that removal of the brain caused a marked diminution in the duration of the feint, although the response could still be induced in de- cerebrate specimens. If a feigning individual be cut in two across the prothorax the posterior part often continues to retain its rigidity for some time and may be thrown back into the death feint again if it is picked up and stroked. Similar results were ob- tained in Belostoma and Nepa by the Severins, who have investigated the role of the nervous system in especial detail. The cataplectic state which Preyer and Verworn found could be induced in decerebrate fowl may be allied to the conditions described above. One marked characteristic of the death feint is an apparent insensibility to pain. De Geer in writing of a boring beetle Anobium pertinax says that “you may maim them, pull them limb from limb, roast them over a slow fire, but you will not gain your end; not a joint will they move, nor show by the least symptom that they suffer pain. A similar apathy is shown by some species of saw-flies (Ser- rifera), which when alarmed conceal their antenne under their body, place their legs close to it, and remain without motion even when transfixed by a pin. Spiders also simulate death by folding up their 214 Studies in Animal Behavior legs, falling from their station, and remaining mo- tionless; and when in this situation may be pierced and torn to pieces without their exhibiting the slight- est symptom of pain.” The Severins tried the ap- plication of heat to Belostoma, but the insect was invariably brought out of its feint and made strug- gles to escape, although it might endure more or less mutilation without making any response. I have found that a feigning Ranatra will allow its legs to be snipped off without betraying the least move- ment beyond an occasional twitch. Similar insen- . sibility has been observed in Nepa (Severin), Carau- sius (Schmidt) and other forms. As has been pointed out by Romanes, Preyer, Verworn, Schmidt and others, the instinct of feign- ing death is doubtless closely connected with much of what has been called hypnotism in the lower ani- mals. Crayfishes, frogs, lizards, certain snakes and many birds and mammals, may by a'very simple process be thrown into an inactive condition from which they are not readily aroused by external stim- uli. In ordinary death feigning the animal falls into its immobile state upon slight provocation; a touch, or even a jar is sometimes all that is required. In| the so-called cases of hypnosis more or less manipv- . lation is necessary. The exciting cause in both cases is generally some form of contact stimulus. In the hypnotism of animals, as Verworn and others have shown, there is diminished reflex irritability, and usually tonic contraction of many at least of the The Instinct of Feigning Death 215 muscles. Similar phenomena are observed in the death feigning of many forms, some of the insects, as we have seen, showing a lack of responsiveness that is truly remarkable. The independent development of death feigning along many different lines of descent makes it prob- able that we must look for the origin of this curious instinct in some fundamental and widespread mode of behavior. In a paper on the death feigning of terrestrial amphipods the writer has suggested that the death-feigning instinct in these forms had its origin in an accentuation of the thigmotactic re- sponse which is such a prevalent trait of behavior among the amphipods in general. It was found pos- sible to establish a series of stages between the typ- ical death feint of the large terrestrial amphipod Talorchestia and the ordinary thigmotactic reactions of the aquatic relatives of this species. In Orchestia palustris, a species not so exclusively terrestrial as the preceding, the body during the death feint is less closely curled up, the appendages are not so closely drawn up to the body, and the feint is not so per- sistent. In the small Orchestia agilis, which lives usually near the water line, the death feint is shown in a somewhat less decided way, while among the aquatic members of the Orchestiide the same trait is manifested by a tendency to curl up and lie quiet when in contact with rocks or seaweed. To one who _ has studied and compared the attitudes and behavior of this series of forms there can be little doubt that the typical death feint of the most terrestrial of the 216 Studies in Animal Behavior species has its basis in the thigmotaxis of the aquatic forms. As the species studied become more terres- trial in habit, the thigmotaxis becomes gradually specialized into a typical instinct of feigning death. Many facts indicate that death feigning in insects and other forms has had a similar origin in the thigmotactic response. It is a rather striking fact that, with very rare exceptions, it requires some form of contact stimulus, it may be but a touch, jar, or even a breath of air, to elicit this instinct. One of the very few exceptions to this rule which has been recorded is afforded by Carausius, whose death feint, according to Schmidt, arises from internal causes, and cannot be induced by any discoverable environmental agency. Should it be definitely estab- lished that this case is truly one of ‘‘autocatalepsy,” as it has been called by Schmidt, it would not be fatal to the supposition that it began originally as a reaction to contact; for it is not without precedent that an instinct having originated with reference to one feature of the environment should finally come to be set into operation by a quite different cause. Those cases of death feigning in which there is a limp and relaxed condition of the musculature, such as occurs in some birds and mammals, may have an origin quite different from that of the more preva- lent cataleptic type. The suggestion that death- feigning had its origin in the partial paralysis pro- duced by fear may perhaps apply to cases such as these, although this explanation cannot, I feel sure, References 217 be extended to the derivation of the typical form of this instinct. While there is simulation of death in both types of behavior we have described, it is prob- able that we have to do with two distinct kinds of reaction differing both in their physiological charac- ter and in their phyletic origin. REFERENCES Darwin, C. Chapter on instinct appended to Romanes’ mental evolution in animals. 1884. Fare, J. H. Souvenirs entomologiques, T. 7. Hormes, S. J. (1) Death feigning in terrestrial amphipods. Biol. Bull. 4, 191, 1903. (2) Death feigning in Ranatra. Jour. Comp. Neur. Psych. 15, 200, 1906. (3) The instinct of feigning death. Pop. Sci. Mon. 72, 179, 1908. Hupson, W.H. The naturalist on the La Plata, 1892. Kirspy, W. and Spence, W. An introduction to entomology: 6th ed., 1846. Louner, L. Untersuchungen iiber den sogen- annten Totstellreflex der Arthropoden. Zeit. allg. Physiol. 16, 373, 1914. Morean, L. H. The American beaver and his works, Phila. and London, 1868. PoLmmantTl, O. Studi di Fisiologia etologica. II, Lo stato di immobilita temporanea (“morte appar- 218 Studies in Animal Behavior ente”’-‘‘Totenstellen”) nei Crostacei_ Brachiuri. Zeit. allg. Physiol. 13, 201, 1912. RoBERTSON, T. B. On the ‘‘sham-death”’ reflex in spiders. Jour. Physiol. 31, 410, 1904. Romanes, J. G. Mental evolution in animals. 1884. SEVERIN, H. H. P., and Severtn, H. C. An ex- perimental study on the death-feigning of Belostoma (-zaitha aucct.) flumineum Say and Nepa apiculata Uhler. Behavior Monographs, Vol. I, No. 3, rg1t. ScumipT, P. Katalepsie der Phasmiden. Biol. Cent. 33, 193, 1913. VeRworRN, M. (1) Tonische Reflexe. Arch. ges. Physiol. 65, 63, 1897. (2) Beitrage zur Physiologie des Zentralner- vensystems. I Teil. Die sogenannte Hypnose der Tiere. Jena, 1898. XII THE RECOGNITION OF SEX OW do the males of the lower animals dis- tinguish the females of their own species from all the rest of the animate creation? Obviously the perpetuation of the race depends on the circum- stance that the male is correctly guided in the choice of a mate. A male beetle or bug will pass by with indifference thousands of other varieties of insects, but in the presence of a female of his own kind his interest is keenly aroused. It almost goes without saying that this power of discrimination is a matter of instinct. It is easily demonstrable in most animals that the element of experience is entirely unnecessary for the proper solution of this important problem. Apparently the male is guided by a sort of elective affinity to the right object upon which to bestow his attentions. What are the signs by which this object is recognized? ; An important factor in the discrimination of sex that naturally occurs to one is the sense of smell. The lower animals, or at least many of them, are influenced by odors to an extent which we with our comparatively obtuse olfactories find it difficult to appreciate. The odors of most species are specific, 219 220 Studies in Animal Behavior and even individuals, in higher forms at least, have an odor peculiarly their own which a bloodhound is able to distinguish from among dozens of others. Differences in odor frequently characterize the two sexes, and hence afford a feasible means of sex dis- crimination. The males of many forms have much more highly developed olfactory organs than the females. The antenne of insects which contain the olfactory sense organs are frequently larger and more complex in the males. In the drone bee, for instance, the olfac- tory pits of the antenne are many times more numer- ous than in the queen or worker. Many male moths have large feathered antennz, whereas these organs are much smaller in the females. It is mainly through the sense of smell that the male moths are able to find their mates, and in some species this sense is developed to a degree that almost surpasses credence. In one of his most delightful essays the French naturalist Fabre tells of the nuptial flight of the males of the large and beautifully colored moth called the great peacock (/e grand paon). A cocoon which was kept in Fabre’s study had produced a female moth which was placed under a gauze cover. In the evening the observer had his attention at- tracted by the call of his young son: ‘‘ ‘Come quick, come and see these butterflies! Big as birds! The room is full of them!’ Several of the large moths had come into the room through the open window. The Recognition of Sex 221 Others had entered the kitchen, and still others were found in various rooms wherever there was a chance for them to enter. . . “It was a memorable night—the Night of the Great Peacock! Come from all points of the com- pass, warned I know not how, here were forty lovers eager to do homage to the maiden princess that morning born in the sacred precincts of my study.” The night was one of black darkness, yet the moths threaded their way through the trees surrounding the house, and came through open windows into darkened rooms without abrading in the least the scaly covering of their wings. But keen as the sense of sight in these insects may be it is not through this sense that the males are drawn toward their intended mates. “When,” says Fabre, “I placed the females in boxes which were imperfectly closed, or which had chinks in their sides, or even had them in a drawer or a cupboard, I found the males arrived in numbers as great as when the object of their search lay in the cage of open work freely exposed ona table. I have a vivid memory of one evening when the recluse was hidden in a hat-box at the bottom of a wall-cupboard. The arrivals went straight to the closed doors, and beat them with their wings, toc-toc, trying to enter. Wandering pilgrims, come I know not where, across fields and meadows, they knew perfectly what was behind the doors of the cupboard.” Fabre cut off the antenne of several of the males of this and other species of moths and found that 222 Studies in Animal Behavior they failed to approach the vicinity of the female. The presence of other odors, which would make an almost intolerable stench in our own nostrils, failed to deter the males in the least from the object of their search. The odor, according to Fabre, seemed to be carried against currents of air, for a rare female specimen of the Lesser Peacock drew numer- ous males which flew with the wind to the place of her confinement. It is scarcely to be wondered at that Fabre considered the sense of smell to depend in part on other means than the wafting of odorous particles, a sort of force acting after the manner of rays of light or X-rays and capable of radiating to a great distance despite adverse currents of air. The réle of smell in sex recognition among the crustaceans is more uncertain. The antennal sense organs which are very probably olfactory in function are in some species much better developed in the male sex. But little is known, however, in regard to the means by which most species find their mates. In some amphipod crustaceans with which the writer experimented a few years ago olfactory stimuli were found to play little or no part in the discrimination of sex. The males of this group have the curious habit of carrying the females about under the body. This act of transportation has no direct reference to the impregnation of the eggs further than to insure the proximity of the sexes when the proper time for fertilization arrives. This occurs soon after the fe- male casts off her skin, when the sperms are depos- The Recognition of Sex 223 ited by the male on the ventral side of the thorax of his mate. After the eggs are fertilized the male continues to swim about with the female as before. “The instinct of the male amphipod ? to seize and retain hold of the female is one of remarkable strength. ‘The male retains his hold, despite all efforts to dislodge him, with remarkable persistence, and will still cling to the female after the posterior half of his body has been cut away. My own obser- vations on the sexual behavior of amphipods relate mainly to three species, Amphithe longimana Smith, Hyalella dentata Smith, and Gammarus fasciatus Say. The sexual behavior of these three species is remarkably similar although they belong to as many » distinct families. The female while carried about keeps remarkably impassive. Her thoracic legs are drawn up, the abdomen held strongly flexed, the whole body assuming as compact a form as possible. She takes no part in swimming; the movement of the pleopods when the body is strongly bent upon itself serves only to keep a current of water passing by the gills. She is carried about like a helpless burden, allowing her vigorous spouse to assume the entire labor of transportation and the responsibility for keeping her as well as himself out of danger. “The efforts of the male to seize the female and get her into the proper position to be carried have the effect of inducing her to throw herself into the 1 Quoted from an article by the writer on “Sex Recognition in Amphipods,” published in the Biological Bulletin, Vol. 5, p. 288, 1903. 224 Studies in Animal Behavior characteristic bodily attitude and remain quiet. The attitude assumed by the female is similar to that observed in the ordinary thigmotactic reaction of amphipods and may, perhaps, be but the same form of response somewhat modified and specialized in relation to the function of reproduction. When the males are torn away from the females they soon seize their partners again and roll them about into the proper position and then proceed on their way in apparent contentment. ‘The female, as soon as seized by the male, curls up and allows herself to be rolled and tumbled about without a show of resist- ance or protest. [he males, as a rule, are larger than the females and usually get their partners into the desired position quite readily; but when a small male attempts to carry a large female he experiences much difficulty. I observed a male Hyalella en- deavoring to carry a female somewhat larger than himself. After seizing the female he would turn her around until she finally came into the proper position for transportation, but owing to the larger size of his partner the male could not reach around her body so as to carry her away. No sooner was the female properly adjusted than the male would lose hold of her round body and the same efforts had to be repeated. During all this performance the female remained dutifully passive. After watching the further struggles of the male for over half an hour I became convinced, although he was not, that he had undertaken an impossible task, and discon- The Recognition of Sex 225 tinued my observations.” That the male amphipods do not distinguish the females by sight was shown by blacking over the eyes of several males and then placing them in a dish with females. It was not long before each male had secured a mate. The possible role of the sense of smell was tested by removing from a number of males the first antenne which contain the olfactory sense organs. After the specimens had recovered from the slight shock of the operation they seized the females and carried them about in the usual man- ner. They reacted in the same way when the second antenne were removed also. In another experiment several females were con- fined within an enclosure of wire gauze which was placed in a dish of water containing several eager males. The males paid not the slightest attention to the females within the enclosure, but after it was raised and the females allowed to scatter through the dish, most of the males were found carrying their mates. “Tf one attentively observes Hyalellas as they are swimming about, it will be seen that the males do not pursue the females, great as their eagerness may be to seize and carry one of the opposite sex. Only when the two sexes collide in their apparently ran- dom movements does the male become aware of the presence of the female. When a male and a female collide, the female curls up and lies quiet while the male makes efforts to seize her. Should two females 226 Studies in Animal Behavior collide they may curl up for a moment, but as they are not seized they soon pass on. When two males meet there is often a lively struggle. Each appar- ently attempts to seize and carry the other, but as neither will consent to remain passive they soon sep- arate. The different reactions of the two sexes to contact with other individuals is the factor which effects the union of the males with the females. Each reacts to the reactions of the other. The male has a strong instinct to seize and carry other individuals of the same species. The female has the instinct to lie quiet when another individual comes into contact with her, especially if she is seized. The instinctive reactions of the two sexes are complementary, and cooperate to bring about and maintain the peculiar sexual association characteristic of the Gammaridea. “If the association of the sexes is brought about by their peculiar modes of reaction to certain contact stimuli, it would seem probable that the only reason why males do not carry other males as well as females is that they are prevented from so doing by the active resistance of their intended mates. I was accordingly led to try the experiment of mutilating some male specimens so that they could no longer make effective resistance to seizure. The large sec- ond gnathopods (the principal means of defense) of several males were cut off and the mutilated indi- viduals were placed in a dish with several males which were recently torn from females. The muti- lated males were soon seized and carried about as The Recognition of Sex 227, if they were members of the other sex. In one case a mutilated male was carried about for over five hours. The mutilated males were more active than females are under the same conditions, and did not assume the same bodily attitude, but nevertheless their captors carried them without any manifest awareness of the deception to which they were sub- jected.” In another group of crustaceans, the Copepoda, the mating instincts are more or less analogous to those of the amphipods. In the copepods, however, the males in seizing the females employ the first an- tenn, which are often enlarged and especially mod- ified for this function. In Cyclops fimbriatus, whose behavior was studied by the writer, the male clasps the female just in front of an enlargement at the base of the abdomen. Males show much eagerness in grasping the females, and they may be poked about roughly with a needle and the posterior part of the body may be cut off without causing them to leave their hold. ‘As the pairs of Cyclops ? swim through the water the males are usually the more active. Frequently the female remains entirely quiet with the appen- dages drawn close to the body, and the body flexed ventrally, allowing herself to be passively carried about by her mate. At other times the female may swim as actively as the male. In general the be- 1 Quoted from Holmes on “Sex Recognition in Cyclops,” Bio- logical Bulletin, Vol. 16, p. 313, 1909. 228 Studies in Animal Behavior havior of the females and their attitude while being carried closely resemble what is found in the Amphi- poda. So also does their behavior when the males come in contact with them and attempt to seize them. The female during the efforts of the male to clasp her around the base of the abdomen usually lies quiet with the appendages drawn close to the body... . “So far as could be detected the males do not seek or follow the females at a distance as Parker con- cluded they did in Labidocera. The association of. the sexes seems to be due merely to chance collisions. Males often attempt to seize other copepods regard- less of sex. The males resist such attempts at seiz- ure and dart quickly away, while the females often stop and submit readily to the clasping propensities of their companions. Several males were injured so that they could not resist seizure, and in many cases they were seized by other males who worked indus- triously until they got their burden clasped around the base of the abdomen in the usual way. These associations did not last long, however; the active males, apparently appreciating that something was wrong, soon swam away. Recently killed females were often seized and in some cases carried about for a while, but they were finally dropped.” There was no evidence that odor determined the sexual behavior of the males. The males paid no attention to a number of females that were enclosed within a tube whose end was covered with wire gauze. In another experiment several females were The Recognition of Sex 229 placed in a tube in which a small plug of loose cotton was inserted a short distance from one end. The males showed no tendency to enter the open mouth of the tube as they might be expected to do if they were attracted by the odor of the females. The ex- periment of removing the organ of smell, which was performed in the case of the amphipods, would be a fruitless one in Cyclops, as the seat of smell is located, to a considerable degree at least, in the same organs that are used for clasping. “It is evident that mating in Cyclops is brought about much as it is in the Amphipoda. The males have a strong tendency to clasp other copepods; the females tend to remain quiet in a condition some- what resembling the death feint while being seized by the males. It is not improbable that olfactory stimuli may cause the males to remain with the fe- male longer than they otherwise would, and they may render the males more prone to seize females than other males, but so far as could be deter- mined by watching the behavior of the animals the specific reaction of the two sexes to certain kinds of contact stimuli is the main factor in bringing about their association.” In the crayfish the studies of Andrews and of Pearse have shown that sex recognition is effected by much the same method as is followed in the am- phipods. Extracts from the bodies of females added to water containing the males did not elicit the least response, Nothing in the behavior of the males indi- 230 Studies in Animal Behavior cates that they are drawn toward the females by the sense of smell. Mating apparently is dependent upon the chance meetings of the sexes. ‘‘During the mating season,” says Pearse, “‘the instinct of the male is to grasp and turn over every crayfish that comes in his way. . . . If this individual is a female of the same species the attempt may meet with suc- cess, but if it is a male or a female of another species the effort at sexual union is usually of short dura- tion.” If males attempt to mate with other males, as they often do, they encounter active resistance, but if a female is attacked she usually remains pas- sive. In fishes the males are frequently distinguished by their more conspicuous coloration especially during the breeding season. The pugnacity and threaten- ing attitudes of the males at this time undoubtedly contribute to their mutual recognition, but there is evidence that the mature males often recognize one another by their peculiar markings. In her account of the breeding habits of the rainbow darter, Miss Reeves records several cases of young dull-colored males being mistaken for females, whereas the larger and more brilliantly colored adults usually recognize one another without difficulty. ‘The more nearly the behavior of a dull male simulates that of a female, as in the case of a male burrowing for food, the more is he likely to be taken for a female. Upon the near approach of the brilliant male the young male erects the first dorsal and rapidly escapes, The Recognition of Sex 221 modes of behavior not observed in the female. It appears, then, that the brilliant fish distinguishes the two by their behavior; a mode of sex recognition pointed out by Holmes (1903) in the case of amphi- pods. In the case of very young males the sex recog- nition must be wholly of this character, while males which already show some little sexual coloration are probably distinguished upon near approach by means of it as well as by behavior.” 1 Among the amphibians the recognition of sex in the frog has been the subject of several interesting experiments by Goltz. In frogs and toads the males clasp the females during the breeding season until the eggs are discharged when the male sheds his sperm over them. What it is that induces the male to discharge his sperm at the opportune moment when the eggs are passing from the female has never been satisfactorily cleared up. The clasping of frogs insures that the male is on hand when his services in fertilizing the eggs are required. The clasping instinct is a temporary one, coming on early in the spring, and then ceasing after the short breeding period is past, when the sexes scatter and pay no further heed to one another’s existence. As is well known, male frogs and toads often clasp various objects during the breeding season. Frogs have been ~ found to clasp fishes the eyes of which they some- times gouge out with their thumbs; and I have taken a male toad industriously clasping an old dried apple. * Biological Bulletin, Vol. 14, p. 35, 1907. 232 Studies in Animal Behavior The instinct to clasp is one of great strength and male toads may suffer their bodies to be cut in two without relinquishing their hold on the female. Correlated with the appearance of the breeding instinct there occurs increased development of the inner digital muscles and certain other parts of the fore legs of the males, a development which Nuss- baum has shown to be checked if the males are cas- trated a considerable time before the onset of the breeding season. Probably as a result of internal secretions of the reproductive glands, parts of the neuro-muscular mechanism become at this time pecu- liarly irritable, so that a particular form of reflex activity is very easily evoked. But notwithstanding this, a frog or toad seldom clasps for long anything but the female of his own kind. Other males may be clasped, but they are usually soon relinquished, while a female is clasped the more firmly the longer she is held. How does the frog distinguish male from fe- male? Goltz has found that blinded frogs discrimi- nate between the sexes as well as normal frogs. After the olfactory nerves were cut he found that males can still distinguish females, so that neither sight nor smell is a necessary element in the recog- nition of sex. Even when the males were robbed of both sight and the sense of smell many of them succeeded in clasping the females among which they were placed. When the females were rendered mute by an operation they were no longer seized. The Recognition of Sex 233 Males, Goltz concluded, are not drawn toward the females through one sense alone, but by means of several senses, no one of which is indispensable. It is a striking fact that a frog whose head is cut in two so as to remove the cerebral hemispheres and eyes will nevertheless continue to clasp a female that is presented to him, while he soon rejects one of his own sex. The bodies of females are commonly plumper than those of the males. May the latter perchance distinguish the females by their form? Goltz tried the experiment of stuffing out the body of a male frog and giving it to another male, but he found that it was soon abandoned. Does the male frog have so delicate a tactile sense that even though nearly brainless he cannot be deceived as to which sex is within his grasp? Goltz is inclined to con- sider that such is the case. It may be open to doubt, however, if the possibility was sufficiently consid- ered that sex recognition may be a result of the behavior of the two sexes, much as it was found to be in amphipods. Despite the interesting experi- ments of Goltz the matter requires further investi- gation before a decided conclusion can safely be drawn. In the birds the sexes may often be easily dis- tinguished by sight, and in many species each sex is doubtless able to recognize the other by this sense alone. The discrimination may be aided by the ob- servation of differences in behavior. There is little 234 Studies in Animal Behavior evidence from the behavior of birds that the sense of smell is relied upon in this matter to any degree. In those birds in which the two sexes are much alike, as in most pigeons, differences in behavior ap- parently afford the chief means by which each sex distinguishes the other. Craig in his interesting ac- count of the expressions of emotions in pigeons * says that “If a cage containing an unmated male ring- dove be suddenly brought alongside another cage containing another ring-dove, of unknown sex, the male becomes highly excited at once, and gives vent to his excitement in all possible ways. First he bows and coos with all his might, and he con- tinues to do so for a long time. ‘Then he charges about the cage, assuming the attitude peculiar to the charge, and frequently repeating the loud kah- of-excitement. At intervals he stops to glare at the strange bird and sometimes to peck at it through the bars, but soon he starts again to bow-and-coo and charge. . . “Tf left beside the stranger’s cage for some hours, the male must sometimes rest and be silent; but even the intervals of rest and silence are broken fre- quently by series of perch-coos. This behavior on the part of the male is useful in that it stimulates the strange bird to respond, and, in responding, to reveal its sex. “Tf the strange bird be a male, it shows similar 1 Journal of Comparative Neurology and Psychology, Vol. 19, Pp. 29, 1909. The Recognition of Sex O35 excitement and aggressiveness. And the two males are sure to fight if they can reach one another. ‘But if the strange bird is a female, she acts far otherwise. She is at first very indifferent, unless she is particularly anxious to mate. And after some days, when she begins to show an interest in the male, she does not give the bowing-coo, nor charge up and down the cage, nor show other signs of pug- nacity and aggressiveness. So far from tending to aggress the male, her conduct is rather an expres- sion of submission to him. She shows a certain excitement; for instance when she utters the kah it is a kah expressive of gentle excitement. But she spends the greater part of her time in alluring the male by means of the nest-calling performance—the nest-calling attitude, seductive cooing, and gentle flip ‘of the wings. She often tries to get through the bars of her cage to the male; and, failing to do so, she sometimes lies down with one side pressed against the bars... . ‘“‘When the male sees the strange bird behaving in this submissive and seductive manner, he loses the intensity of his pugnacity; though he always con- tinues to be masterful. He spends less time now in the bowing-coo and more time in nest-calling and in trying to get to the female.” In the mammals the sense of smell plays a much larger part in the recognition of sex than it does in birds and the lower vertebrates. Not only is the sense of smell as a rule acute, but scent glands 236 Studies in Animal Behavior of various kinds are of frequent occurrence in one or both sexes, and frequently the secretion of these glands is exceptionally abundant during the breed- ing season. Commonly scent glands are better de- veloped in the male sex. The strong odor of the male goat is notorious. In the male elephant there are glands on the side of the face which, in the breeding period, enlarge and emit a milky secretion. In the males of many species of deer and antelope there are facial glands that are especially active in the rutting season. Other species have scent glands on the feet and limbs, or near the tail. It is not improbable that the secretion of these glands, while not particularly agreeable to ourselves, may have an alluring influence on the opposite sex of the species concerned. ‘There is abundant evi- dence that different species of mammals are able to recognize their own kind through the sense of smell, and it is a well-known fact that many mam- mals are exceedingly quick to detect the scent of an approaching enemy. Any one who has watched the behavior of dogs in taking a sniff at their different acquaintances, or in getting a fuller olfactory im- pression of a stranger, will realize somewhat to how great an extent experience with odors makes up the dog’s mental world. Many facts indicate that mammals distinguish the opposite sex of their own species through the sense of smell, but as the sexes frequently differ in external appearance they are undoubtedly able to recognize one another by References 237 sight. A certain familiarity with the habits of street curs will convince one, I think, that the element of behavior, as in some of the cases previously de- scribed, plays a certain réle also. The recognition of sex has been little analyzed in the mammals. The problem is more complex than in lower forms owing to the higher development of the mammalian mind, and the fact that several dif- ferent senses are usually involved. REFERENCES Anprews, E. A. Conjugation in the crayfish, Cambarus affinis. Jour. Exp. Zool. 9, 235, I9gII. Banta, A. M. Sex recognition and the mating behavior in the wood frog, Rana sylvatica. Biol. Bull. 26, 171, 1914. Craic, W. The expression of emotion in the pigeons. I, The blond ring dove (Turtur risorius). Jour. Comp. Neur. Psych. 19, 29, 1909. Fapre, J. H. Souvenirs entomologiques, 7 serie. Gottz, F. L. Beitraige zur Lehre von den Funk- tionen der Nervenzentren des Frosches. Berlin, 1869. Homes, S. J. (1) Observations on the habits of Hyalella dentata. Science, N. S. 15, 529, 1902. (2) Sex recognition among amphipods. Biol. Bull. 5, 288, 1903. (3) Sex recognition in Cyclops. Biol. Bull. 16, 313, 1909. Parker, G. H. Reactions of copepods to vari- 238 Studies in Animal Behavior ous stimuli, etc. Bull. U. S. Fish Com. 21, 103, IgO!. Reeves, C. D. The breeding habits of the rain- bow darter (Etheostoma ceruleum Storer), a study in sexual selection. Biol. Bull. 14, 35, 1907. XIII THE ROLE OF SEX IN THE EVOLUTION OF MIND HE reason for the existence of sex is one of those biological problems whose solution seems as remote as it did a century ago. Many remark- able discoveries have been made in regard to the microscopic structure and development of the germ cells in both plants and animals. We have learned much of the general biology of sex, and the prob- able evolution of sex in the organic world. And substantial progress has been made with the old problem of the determination of sex. But to the question, Why came there to be two sexes at all? or in other words, Why do not organisms continue to reproduce asexually as it is probable they once did? we can only offer answers that, to say the least, are very hypothetical. While the fact that sex is absent in the lowest forms of life indicates that evolution has proceeded at least a certain distance without its aid, and sug- ~ gests the possibility of the evolution of sexless forms of a high degree of organization, yet the general prevalence of sex, with but rare exceptions, in all but the most primitive organisms points to the con- clusion that sex has played a fundamental réle in 239 240 ' Studies in Animal Behavior the evolution of the organic world. It is doubt- less futile to conjecture what the organic world would have been like if the institution of sex had never been evolved. Even if the processes of varia- tion and selection had gone on to the same extent— which is scarcely probable—the absence of sex would certainly have given to evolution a very different direction from that which was actually followed. Many of the most complex of the structural ar- rangements of organisms have especial reference to securing the meeting of the germ cells. The color and scent of flowers, and their many and beautiful adaptations to effect cross fertilization would never have appeared if plants were propagated solely by the asexual method. In animals the structural pe- culiarities associated with sex are, as a rule, among. the most complex features of the body. Correlated with these structures we find mating instincts which frequently manifest themselves in complex modes of behavior. More acute senses have been evolved in many cases very largely in relation to securing the meeting of the sexes. The large antenne of male moths and several other insects, the larger eyes of the common drone bee, and the auditory appara- tus of the male mosquito are a few of the numerous illustrations of this fact. The various kinds of apparatus in insects for mak- ing sounds which are found in crickets, locusts, and cicadas are devices for drawing the sexes together, and the complementary development of auditory or- The Réle of Sex in the Evolution of Mind 241 gans in the same insects has doubtless been greatly furthered through the evolution of these structures. The primary function of the vocal apparatus of the vertebrates was probably to furnish a sex call, as is now its exclusive function in the Amphibia. Only later and secondarily did the voice come to be em- ployed in protecting and fostering the young, and as a means of social communication. And the evo- lution of the voice in vertebrates doubtless influ- enced to a marked degree the evolution of the sense of hearing. It is not improbable, therefore, that the evolution of the voice, with all its tremendous consequences in regard to the evolution of mind, is an outgrowth of the differentiation of sex. In cases of degeneration through parasitism or other causes the female often proceeds much farther on the downward path than the male. In the scale bugs, for instance, the females have lost their wings and many other structures, while the adult male re- mains an active and graceful winged insect. The necessity for finding the female has kept the male from undergoing the degeneration that has over- taken the other sex. Much of the elaborate organization of the imago state of insects has reference to activities directly or indirectly concerned with mating and depositing the eggs in the proper environment for the develop- ment of the young larve. There is a relatively long nymphal or larval period chiefly devoted to the vegetative functions of assimilating nutriment, and 242 Studies in Animal Behavior growth; in many species the imago takes no food or need take none, before the eggs are fertilized and laid; and in several forms the mouth parts have become so atrophied that food taking is impossible. Some insects mate soon after they emerge from the pupal covering. In the May-flies, which live but a short time in the winged state in order to mate and deposit their eggs in the water, it is probable that the imago stage would long ago have disappeared were it not retained as a means of effecting the union of the sexes. So also with many other insects. In the winged state numerous new enemies are encount- ered and many lives are lost; in the pupa stage, which prepares for it, there is commonly an exten- sive tearing down of old structures and the building up of new ones during which the insect is helpless against many enemies and parasites. There are compensatory advantages in the possession of the imago stage in scattering the species into new re- gions, and in many other ways in the different groups, but were it not for the necessity for preserving the mating activities which occur in this period of the insect’s life-history, it is probable that the complex organization of the adult state would very fre- quently have degenerated, or even been lost, if it had not failed to develop at all. The mating activities are almost everywhere among the most complex performances of an ani- mal’s life. The opposite sex must be distinguished from all other creatures and responded to actord- The Role of Sex in the Evolution of Mind 243 ingly. Often pursuit and capture or winning over are the necessary preliminaries of mating. All this puts a premium so to speak on the sharpening of the senses, the development of strength and acute- ness, and the evolution of higher psychical qualities. Consider the mating activities of crustaceans, the courtship of spiders, the breeding activities of fishes, and still more the elaborate wooing of male birds, and it will become manifest how greatly the insti- tution of sex must have stimulated the evolution of more complex modes of behavior. All the facts here cited are trite enough even to the non-biological reader. But while it is sufficiently evident that the differentiation of the sexes has pro- moted the development of behavior in relation to mating, it may be well to point to the enormous in- direct consequence of this development in respect to the evolution of mind in general. In the evolu- tion of behavior one kind of instinct grows out of another just as new organs are usually formed by the elaboration of some pre-existing structure. A general elaboration of instinctive reactions in re- gard to any one sphere of activity affords a basis, therefore, for the differentiation of more complex or specialized behavior in respect to other activi- ties. The primary function of the voice, as has al- ready been pointed out, was to serve as a sex call. Later it became the means of various instinctive forms of communication and finally afforded the medium of articulate language. Had it not been for 244 Studies in Animal Behavior its value in the mating of the lower vertebrates the voice might never have been evolved and man never have become man. While the specialization of senses, which, in cer- tain cases at least, has been carried on mainly for sexual purposes, naturally afforded a basis for the elaboration of many instincts, it is practically im- possible to trace in detail how various instincts, sex- ual and other, may have acted and reacted on one another’s development. But we can discern enough of the influence of sex differentiation on the evolu- tion of behavior to feel assured of its importance. The necessity of solving the one problem that con- fronts all dicecious animals which do not simply shed their sexual products at random into the water has kept behavior in one sphere up to a certain mini- mum standard. The male must find and impregnate the female, and this fact sets a certain limit to his degeneration, at least in some period of his life. But besides acting as a check to degeneration, the necessity for mating has, in general, been a con- stant force making for the evolution of activity, en- terprise, acuity of sense, prowess in battle, and the higher psychic powers. We cannot pretend accu- rately to gauge its role in the evolution of mind, but it has evidently been a factor of enormous potency. XIV THE MIND OF A MONKEY IZZIE was first seen in a store on Market Street, San Francisco, where she was confined in a cage with a small puppy which was put in for company. She was a specimen of bonnet monkey, Pithecus sinicus, and she had been recently imported from India, so her owner averred, but during her short captivity she had come to be quite tame and tractable. A few days later she became the prop- erty of the University of California, and was kept in a cage especially constructed for her reception in a sort of storeroom belonging to the department, of zoology. Owing perhaps to the strangeness of her new surroundings, or to the loss of her old as- sociates, Lizzie frequently gave vent to a plaintive cry, but she seemed to be appeased when any one came near. When let out of her box she began to scamper about, climbing up tables and other objects, and examining things critically all about the room. If approached she would often utter a sound resem- bling a bark and stand with her mouth open in a threatening attitude, at the same time being on the alert to make her escape. She proved to be re- markably agile, even for a monkey, and very quick 245 246 Studies in Animal Behavior to discover the least movement anywhere within her range of vision. She would move about almost con- stantly, but her attention was not directed to any one object for more than a few seconds at a time. Lizzie showed a strong aversion to being taken in the hands, although she soon came to jump upon my shoulder and ride about there quite contentedly. Often when I stretched out my hands to seize her she would bound past them to my arm and quickly scamper to my shoulder. It was difficult to get hold of her in that situation, for she would clamber about over my body in a very nimble way in her efforts to avoid seizure. She was fond of diving into my pockets and extracting articles therefrom and then scampering away with them. She appeared to take a certain pleasure in being pursued for the recov- ery of the stolen property. Most things which she took went straight to her mouth. She was especially fond of chewing up lead pencils, and took an ap- parent delight in breaking things or pulling them to pieces. After a detailed investigation of an object for some minutes, during which she turned it over and over with her hands and feet—for she was al- most as facile in grasping things with her feet as with her hands—she usually wearied of her play- thing and gave it little further attention. This sort of intellectual curiosity afforded her many things with which to occupy herself; and when no other object engaged her attention she would frequently busy herself with inspecting her own person in the The Mind of a Monkey 247 pursuit of possible parasites. One marked trait of Lizzie’s behavior was the ease with which she became alarmed at any unusual object or occurrence. After some months of ac- quaintance, when she would sit contentedly on my shoulder, any quick movement would inspire her with fear. A certain instinctive dread of being taken un- awares seemed to be an ineradicable part of her ‘mental make-up. Bred to a life of continued watch- fulness and fear in the forests of her native home, she was gifted, to a very unusual degree, with the faculties that make for the ready detection and avoidance of danger. For keenness of perception, rapidity of action, facility in forming good prac- tical judgments about ways and means of escaping pursuit and of attaining various other ends, Lizzie had few rivals in the animal world. She frequently surprised me by getting out at a half-opened door which I thought I had effectually guarded, or in grab- bing a bit of food from me which I was confident she could not reach. Her perceptions and decisions were so much more rapid than my own that she would frequently transfer her attention, decide upon a line of action, and carry it into effect, before I was aware of what she was about. Until I came to guard against her nimble and unexpected maneuvers she succeeded in getting possession of many apples and peanuts which I had not intended to give her except upon the successful performance of some task. In disposition Lizzie was gentle and tractable, and - 248 Studies in Animal Behavior did not make more than a rather playful pretense of biting one’s hand. Of affection or attachment to any one, such as has been described in other kinds of monkeys, Lizzie showed scarcely a trace. She seemed to enjoy the presence of people much as she would be gratified in examining a new kind of object; the pleasure she derived was an intellectual one rather than an emotional satisfaction such as a dog takes in his master. When she was irritated, which was easily done, she would give a sort of bark and face one with an open mouth and general attitude of attack. Fits of temper wore off very quickly, for she was very changeable in her moods as well as in her mental pursuits. She was also quickly over her fears. With her, sufficient not only for the day but for the moment was the evil thereof. She wasted no time in retrospection; she lived en- tirely in the present, and in one of very narrow span. While Lizzie was a most admirably efficient little mechanism for getting on in life under the con- ditions of a tropical forest, she proved to be quite stupid when tested according to certain other stand- ards. In order to get a clearer insight into her mentality, recourse was had to a number of experi- mental tests. The front of Lizzie’s cage was made of vertical bars which were far enough apart to allow her to reach out her arm between them. A board was placed just outside her cage and a piece of apple put on the board beyond her reach. Lizzie grabbed at the apple, pushing the board to one side. The Mind of a Monkey 249 Then she tried to seize the board by one end and pull it toward her, but as the board was a little too heavy for her to move well in this manner, a nail was driven in the middle of the end of the board nearest the cage to serve as a sort of handle. When > € cage Fic. 11.—Diagram of Lizzie’s cage with the board B, on which food was placed. nn, position of nails. board and apple were placed as before Lizzie reached immediately for the nail, pulled the board in and got the apple. A repetition of the same ex- periment was followed at once by the same result. During the third trial Lizzie attempted to seize the board by the side and pushed it away out of reach. When the board was replaced she pulled it by the y 250 Studies in Animal Behavior nail and got the apple, as she did also at the next trial. In these experiments, even at first, Lizzie did not reach for the apple directly. She seemed to appre- ciate from her inspection of the situation that the apple could not be secured in this way. Her first efforts were directed to the means of attaining the desired end, and when the nail was driven into the board she seemed to apprehend at once how it could serve her purpose. There was no employment of the method of trial and error; there was direct ap- propriate action following the perception of her re- lation to board, nail and apple. After the fourth trial, when the board was in its usual position and before the apple was on it, Lizzie reached out and pulled it in. In the fifth trial, when the apple was replaced, she seized the board by the side and pulled it in after considerable effort and got the food. Then the board was replaced with no apple on it, but it was pulled in again in appar- ent expectation of the usual reward. This futile performance was repeated several times. Finally Lizzie grew weary of her wasted efforts and would no longer respond. Then a piece of apple was placed about six inches to one side of the board. After making an ineffectual attempt to reach the apple directly, Lizzie seized the board and pulled it in. She did this six times, after which she sat looking at the apple and whining. Then I placed the apple on the board, which was immediately pulled in by The Mind of a Monkey 251 the nail. After her appetite was whetted another piece of apple was placed six inches to one side of the board as before. Lizzie expectantly pulled the board in and repeated the performance six more times, but her actions became slower with each dis- appointment, until after the sixth trial she gave the board up and tried to reach the apple directly. Then I held the apple near the cage to give her a smell of it and replaced it near the board. Being thus stimulated, Lizzie pulled the board in by the nail three times, when she gave up the task. After being tempted as before she pulled the empty board in three times. In these experiments Lizzie showed that she had associated the act of pulling in the board by the nail with obtaining and enjoying the apple. But her persistence in pulling in the board when she could clearly see that the apple was several inches away from it showed that she exercised little discrimina- tion, and indicated that the associations she had formed were of a rather vague and hazy kind. In another experiment I placed the apple further out on the same board so that she would be unable to reach the food when the near end of the board was against the base of her cage. Lizzie pulled the board in at once and reached for the apple. Finding it too far out, she pushed the end of the board sidewise, at the same time keeping it against the base of the cage. This brought the apple nearer and she got it. The experiment was repeated sev- 252 Studies in Animal Behavior eral times and Lizzie solved her problem each time with little or no hesitation, as in the first trial. The problem was then made a little more difficult by placing the apple still farther out on the board so that she could not reach it even when she had pushed the end of the board as far to one side as the limits of her cage would permit. When she had pulled the board in and to one side, finding that the apple was still out of reach, she tried to seize the board by the side and to pull it in sidewise. It was too difficult for her to get a good hold of the board in this way, and her attempts were not suc- cessful. I then drove a nail near the middle of the board. Getting the apple involved pulling the board to the cage by the first nail, pushing it then to one side so as to bring the second nail within reach, seizing the board by the second nail and pull- ing it sidewise toward the cage until the apple was sufficiently near. At her first trial Lizzie pulled the board in by the first nail, then pulled it sidewise, and tried to seize the edge of the board. Appar- ently by accident her hand struck the second nail, which she seized at once, and by its means pulled in the board and got the apple. In the second trial Lizzie pulled the board in and to the left, then © reached immediately for the second nail and pulled in the board toward her cage. In several subse- quent trials she secured the apple in just the same way. The problem was solved perfectly after the first trial. The Mind of a Monkey 253 In another set of experiments Lizzie was given a vaseline bottle containing a peanut and closed with a cork. In accordance with her instinct to bite at new objects Lizzie attacked the cork with her teeth, pulled it out and tried to chew it, holding the bottle meanwhile in one hand; then she noticed the nut when she transferred the cork to her feet, and tried to reach the nut, but the neck of the bottle was too small for her hand to enter. On turning the bottle over the nut dropped out unobserved and I replaced it and put in the cork. Lizzie immediately drew the cork and held it in her hind feet while she tried: to reach the nut with her fingers. Finally, when she was holding the bottle upside down, the nut came within reach of her fingers and she got it out. When given another nut in a corked bottle she pulled the cork and tried to reach the nut with the bottle up- right, but in the course of her efforts she turned the bottle over so that the nut fell down within reach, when she got it. Without describing in detail her subsequent trials, I may say that Lizzie gradually came in the course of fifteen trials to turn up the bottle very soon after she received it and to get the nut much more quickly than at first. She never came to turn the bottle over and let the nut drop out. She was too busy trying to reach it with her fingers to get it by the easiest method. Even after she had come to get the nut rather quickly she often spent considerable time in attempting to reach the nut when the bottle was held \ 7 @ _ Oy Sage OF OY \ 254 Studies in Animal Behavior upright. She did not pick out the essential acts that led to success. She perceived that the nut could be secured by going through a certain series of mo- tions, and the useless movements were gradually eliminated with an average shortening of the time necessary to gain the desired end. So far as her progress is concerned after she had removed the cork from the bottle, she gave no evidence of clearly perceiving how anything that she did furthered her purpose. Apparently she did not clearly apprehend that if she turned the bottle upside down the nut would fall down within reach of her fingers, al- though she had seen the nut fall dozens of times. In the course of her intent efforts her mind seemed _ so absorbed with the object of desire that it was never focussed on the means of attaining that ob- ject. There was no deliberation, and no discrimi- nation between the important and the unimportant elements of her behavior. The gradually increasing facility of her performances depended on the appar- ently unconscious elimination of useless movements. The previous experiments were modified by giv- ing Lizzie a nut in a screw-cap Mason jar without a cover. She could easily reach into the wide mouth and get the nut, but she picked up the jar instead and turned it about. Having accidentally dropped the jar, she scuttled away in alarm, but she cautiously approached it again, turned it over and got the nut. Then she picked up the jar, carried it to her perch, rolling it over and over with her hands and feet in The Mind of a Monkey 255 various ways. I took the jar and put another nut in it, but Lizzie continued to play with the jar and let the nut drop out unobserved. When the nut was replaced Lizzie tried to get it by biting the glass; in the course of her turning the bottle around, the nut dropped out and she picked it up. When an- other nut was put in Lizzie reached in at once and got it. Another nut was obtained in the same way, but at the next trial she turned the jar around in various ways until the nut fell out; and in numerous other trials on different days she sometimes got the nut by reaching it directly and at other times by turning the bottle around until the nut dropped out. Fifty or more trials did not teach her to secure the nut at once by inverting the bottle. While she came to get the nut by reaching into the jar more often than she did at first, she did not settle down to any uniform method of procedure. When a nut was placed in the jar and the cover screwed on very loosely, Lizzie tried to pull the cover off by using her hands and teeth. After much effort she succeeded and held the jar with a hand and a foot and the cover with the other hand. The novelty of the cover engrossed her attention and she let the jar drop. Soon she went to the jar, reached in and got the nut, and then resumed her investiga- tion of the cover. Another nut was placed in the jar and the cover screwed on very loosely as before. Lizzie took the jar to her perch, worked the cover off with her hands 256 Studies in Animal Behavior and teeth, and then reached in and got the nut, hold- ing the jar upright with her‘feet. The next trial resulted in practically the same way. The cap of the jar was then screwed on farther. Lizzie at- tacked the jar industriously and finally removed the cover, although working quite unsystematically. The cover was put on as before and Lizzie worked at it about fifteen minutes, getting more and more ex- cited’ and impatient over her lack of ‘success; some- times she tried to bite through the glass at the lower edge. After turning the cover this way and that she finally unscrewed it‘and got the nut. After numerous trials Lizzie never learned to unscrew the cover by turning it around uniformly in one direc- tion. She simply worked it back and forth until it happened to become entirely unscrewed. Lizzie: was then’set to the task of getting food out of a small box. “Two sides of the box were made of strong wire netting; the rest was wood. In one corner was a small door which could be fas- tened by'a hook passing through a small screw eye. In the first experiments a piece of apple was placed in the box and the door, which stuck rather tightly, was left unhooked. Lizzie looked at me while I put the food through the door and she opened the door at once and got the food. She did the same at the second trial, after which, when the food was replaced, the box: was turned so as to lie on an- other side. This seemed to'disconcert Lizzie and she tried biting and clawing'at the wire netting, and The Mind of 'a Monkey 257 turning the box over and over until she became dis- couraged. I recalled her’to the task: by tapping: on the ‘box, but evoked only feeble efforts. When I opened and closed'the door Lizzie observed me and went at‘once to the door and got the apple. Then I replaced the apple and closed the door and put the box in another position. Lizzie attacked the box in'various places and then desisted. Soon she looked at the box, went to it'as if-an idea struck her, and tried to pull the door open by using hands and teeth; finally, after some tugging, she succeeded. After a few more successful trials the door was fastened with the hook. Lizzie attacked the door with hands and teeth and turned the box over and over and often tried to get'the apple'through the wire. A renewed attack on the hook enabled her to get the door open | and get the apple. The next trial on the succeeding day was followed by much the same method of at- tack. After biting at the hinges and various other parts of the box Lizzie loosened the hook and opened the door. Not to weary the reader with the recital of Liz- zie’s misdirected efforts and slow progress, it may be said that she gradually came°to concentrate her efforts on the door, but even after thirty trials she would bite atithe hinges and ‘edges of ‘the door, and not infrequently‘ she would turn the box over and bite at the wire netting. In all of her efforts at the hook she never learned to’ pull it to one«side. She simply tugged at it this way:and that-with her 258 Studies in Animal Behavior teeth until it came undone. The mechanism of the thing, how the hook stood in the way of opening the door, she could not understand, simple as it was. When a button was substituted for the hook her mode of attack was much the same; and her prog- ress, such as she made in the course of thirty trials, was after the same slow method. She never per- ceived that when the button was turned in one di- rection it left the door free to come open, and that it prevented the door from coming open when it was in another position. She bit and worried away at the button, and pulled at the door until she got it open and got her food. The idea of the thing never got into her head. When both the hook and the button were used Lizzie had a very hard time to get her food. Oc- casionally after much varied and fruitless effort she would succeed. If she got the button turned right she would usually turn it the wrong way before she undid the hook. The experiments would probably have discouraged her observer had they not usually wearied their subject before she met with success. There was little hope that she would be able to solve more complex problems. A peanut that was hung below her at the end of a cord she obtained by pulling up the cord, hand over hand, the very first time she saw it. I tried to teach her to use a stick to pull in food with, as monkeys have sometimes been described as doing, but met with no success. Placing a bit of food out- The Mind of a Monkey 259 side the cage, I poked it about with the stick so as to give her a suggestion of how the stick might be employed to move the food within reach, but al- though the act was repeated many times, Lizzie never showed the least inclination to use the stick to her advantage. In fact, she never exhibited the least tendency to use any object as a tool. Next I tried suspending a piece of food beyond her reach and giving her a light box upon which she might mount and get the food. She did this readily enough when the box was in the right posi- tion. Then the box was pulled to one side in or- der to see if she would pull it back so that she could get upon it and reach the food. Although I fre- quently moved the box about to give her the sug- gestion and often put it in the proper place to en- able her to get the food, the idea of using the box in the way described never seemed to occur to her. Experiments with Lizzie were brought to a close by her death, but the results obtained were sufficient to give some insight into the nature and limitations of her mental endowments. While gifted with re- markably quick perception and in certain respects power of rapid judgment, nothing in her behavior gave any indication of the use of abstract or gen- eral ideas, or of deliberate reasoning. Neither did she exhibit the least tendency toward imitation, al- though I am not prepared to say that further ex- perimentation might not have revealed some evi- dence of this faculty. Some things, and even sim- 260 Studies.in Animal: Behavior ple things, she apparently: learned by the. primitive method of; the. gradual elimination of useless ,move- ments. after attaining: a chance. success. This type of learning is the: ane, mainly, followed by. the less- developed mammals, but in the: apes the curve of learning: simple: things. usually shows: a, sudden de- scent from the start. One-reason for her compara- tively. slow progress in the experiments with. the boxes. and the bottles:is, I suspect, that in her eager- "ness to attain the desired. end. her attention, was never strongly directed to the means employed. When we attempt to.solve a puzzle we direct our attention.to the means. we employ and pass judg- ments upon, them, but Lizzie. never. discovered the value of paying. attention to method: Her impul- siveness and activity stood in the. way of. her at- taining any results:that required a small amount. of. deliberation. The perception of very simple relations. usually escaped her. She never clearly perceived that a hook could: be unfastened by. simply. pulling it to one side, that.a button would not hold a door closed when turned in a certain position; she probably never became clearly aware that when a bottle was turned upside down its contents would fall out. As we know these things, they involve a certain pre- vision, or representation to ourselves of how cer- tain things might happen if certain, conditions were. fulfilled. But this power was but slightly, developed in Lizzie’s mind. There are more indications of it The. Mind of, a Monkey 261 in Lizzie’s performances in pulling in the board by the two nails. The quickness with which she learned the elements of the trick indicated that she perceived the way in which it might be done by simply in- specting the situation. But we should be cautious in our interpretations, because it was not known how near such actions might have been to her previous experience. Had she, for instance, been used to pulling in branches with fruit attached to them, pull- ing in the board might have been a particular ap- plication.of some of her previous activities for which she may have had a strong instinctive bent. While it may not be safe to deny to Lizzie a certain amount of prevision in her performances with the board, we should hardly be justified in say- ing that they necessarily involved: the drawing of an explicit inference. Should one ask if Lizzie were able to reason, the answer would have to depend: on - how reason were defined. That some of her acts are the outcome of. simple inference, though per- haps not explicitly formulated in her mind, is quite probable. Even perception, as Spencer, Binet, and others have shown, is allied to inference; and Liz- zie’s behavior evinces a much closer approach to the rational type than does the process of simple perception. Her behavior does not indicate so high a degree of mental development as that of several other monkeys that have been the subject of ex- periment. Whether her relative ineptitude for cer- tain tasks is an individual peculiarity or a trait char- ~ 262 Studies in Animal Behavior acteristic of her species cannot be stated with any assurance. As I have remarked in another work, ‘We are apt to overestimate the importance of the ability to reason as if it were the chief thing of value in intelligent behavior. There are other mental traits which may enable an animal to get what it wants better than an increment of reasoning power. Gen- eral activity, power of attention, interest, quickness of forming associations, delicacy of discrimination, duration of memory, and the ability to form com- plex associations are all of the utmost importance in many situations of an animal’s life. . . . Give a fox greater power of inferential thinking, but de- crease his alertness, curiosity, suspiciousness, and quickness of perception, and he might fall a victim to the hunter while his mind was employed on some other subject.” Possibly more intelligence of the _human sort would have been a positive drawback under the conditions of Lizzie’s natural environ- ment. INDEX Allen, B. M., 188 Ameeba, behavior of, 32, 127, 184 Amphipods, phototaxis in, 57, 58 Andrews, E. A., 229 Anemones, behavior of, 125-127 Aquinas, St. Thomas, 14, 15 Arenicola larvae, phototaxis in, 56, 57 Aristotle, 11, 12, 15 Bain, A., 45, 133, 134, 139, 163, 164 Balanus larve, phototaxis in, 98, 99, 102, 105 Baldwin, J. M., 28, 30, 133 Bancroft, F. W., 89, 107 Bauer, V., 106 Bert, P., 53 Belostoma, death feigning in, 202, 209-214 Binet, A., 177 Bohn, G., 125 Bonjeant, Father, 16 Brundin, M., 80, 81 Bunsen-Roscoe Law, 89, 90 Butterflies, orientation of, 86- 88 Carpenter, F. W., 93 Carausius, death feint, 209, 214, 216 Cells, behavior of, 177 ff. Celsus, 12 Chloroplasts, reaction of to light, 96, 97 Cicero, 18 Child, C. M., 166-169 Cole, L. J., 65 Compensatory motions, 63-66, 84 Condillac, E. B., de, 19 Copepods, sex recognition in, 227-229 Craig, W., 234, 235 Crayfish, intelligence of, 129, 136 Cytotropism, 180 Daphnia, phototaxis in, 98, 102, 105-108 Darwin, Ch., 25-28, 47, 51, 199, 205 Darwin, E., 17-19 Davenport, C. B., 113 Death feigning, 197 ff. DeCandolle, A., 52 De Geer, Ch., 213 Descartes, R., 15, 16, 21, 22 Dewey, J., 10 Dice, L. R., 102, 103, 105, 106 Differential sensibility, rédle of in orientation, 82-90 Driesch, H., 181 263 264 Drosophila, effect of intense light on, 93, 94 Earthworm, phototaxis in, 65, 71-73, 75-77, 113 Eimer, O. E., 28, 122 Electrotaxis, reversal of, 107 Epithelial cells, behavior of, 184-187 Eudendrium, effect of light on, 90 Euglena, orientation of, 89 Ewald, W. F., 90, 102 Fabre, J. H., 38, 197, 198, 212, 220-222 Fasten, N., 192 Fiddler crabs, phototaxis in, 81 Fishes, parental care in, 140, 143 recognition of sex, 230-231 rheotaxis in, 64, 65 Fiske, J., 46 Fly larve, phototaxis in, 74-77 Forel, A., 121 Francé, R. H., 28 Frogs, sex recognition in, 231- 233 Galen, 12 Gassendi, 17. Geotaxis, 61 Goltz, F., 231-233 Goodspeed, T. H., 107 Graber, V., 53 Groom, T. T., 98 Groos, K., 27, 30 Haeckel, E., 28, 177 Hall, G. Stanley, 30 Index Harper, E. H., 75, 76, 106 Harrison, R. G., 185, 189 Hegner, R. W., 188 Heliotropism, 52, 54, 96 Hobhouse, L. T., 33, 130, 134, 135 Holmes, S. J., 71-76, 80, 94, 114, 169 ff., 183, 185-187, 193, 201-206, 209-211, 213, 215, 292-298, 231 Hudson, W. H., 206, 207 Hume, D., 120 Hyalella, sex recognition in, 223-297 Hydra, behavior of, 125, 128 Hypnotism in animals, 214 Incubation, origin of, 41, 42 Inhibition, 131, 133-136, 139 in tropisms, 113-116 Instinct, analysis of, 30, 31, 51 origin of, 25, 26, 122, 193 Intelligence, beginnings of, 120 ff. critical study of, 33, 34 Jackson, H. H. T., 105, 106 James, W., 128 Jennings, H. S., 70, 71, 76, 89, 126, 127, 156, 158 Jensen, P., 161 Kirby, W., 199 Kirkpatrick, E. A., 30 Lamarck, J. B., 22-24, 122 Lamarckian factor, 28, 29, 160- 164 Learning, problem of, 139 ff. Leech, phototaxis in, 71, 73, 82 Index Leibnitz, G. W., 17 Leptoplana, behavior of, 167, 168 Leucocytes, behavior of, 189-193 LeRoy, G., 17, 19, 22 Lewes, G. H., 122, 123 Loeb, J., 31, 53-55, 69, 17, 78, 81, 84, 89,90, 98, 101, 102, . 105, 113, 121, 183 Loeb, L., 185 Loxophyllum, behavior of, 125, 169-174 Lubbock, Sir. J., 53 Lyon, E. P., 64 Malebranche, 16 Mammals, sex recognition in, 235, 240 Massart, J., 101, 190 Mast, 50, 56, 75, 76, 84, 89, 99, 109-111 McGinnis, M. O., 106 McGraw, K., 84, 85 Michener, E. R., 105, 106 Monkey, intelligence of, 245 ff. Morgan, C. Lloyd, 27, 28, 34, 121, 129, 177 Morgan, principle of, 34, 79, 130 Morgan, L. H., 207 Moore, A. R., 105, 107 Moore, B., 108, 109 Moths, sex discrimination in, 220-222 Nepa, death feint in, 209, 210, 212, 214 Nerve cells, behavior of, 188, 189 Notonecta, phototaxis in, 61, 80 265, Oltmanns, F., 99. Oppel, A., 185 Orchestia, phototaxis. in, 57, 80- 82, 100, 101, 102, 105 Orientation, 54, 56-61, 69 ff. Pain, relation to learning, 131- 137, 140, 143 ff. Paley, W., 20 Paramecium, behavior of, 156, 157 electrotaxis of, 107 Parental care, 34 ff. Parker, G. H., 89, 103, 104, 228 Parmelee, M. F., 30 Pawlow, J. P., 150 Pauly, A., 28 Pearl, R., 112 Pearse, S. A., 229, 230 Pigeons, recognition of sex, 234, 235 Pigment cells, behavior of, 182- 184 Planarians, 166-169 Plato, 12 Pleasure, relation to learning, 131-137, 140, 143 ff. Pliny, 12 Plutarch, 12 Porphyry, 12 Preyer, W., 214 Protozoa, behavior of, 32, 33, 169 ff. Radl, E., 63 Ranatra, death feigning of, 201, 209-211, 213, 214 phototaxis in, 59-62, 80, 94, 95, 102, 104, 108 behavior of, 112, 266 Random movements, 164 réle in orientation, 70-78 Reason in animals, 9, 259-262 Reeves, C. D., 230, 231 Regeneration and __ behavior, 166 ff. Reimarus, S. H., 19, 20 Rheotaxis, 64, 65 Rhumbler, L., 180 Robertson, T. B., 212, 213 Romanes, G. J., 26, 27, 28, 53, 79, 122, 214 Roux, W., 180 Royce, J., 66, 67 Sachs, J., 52, 53 Schmidt, P., 209, 214, 216 Severin, H. C. and H. H. P., 209, 210, 212, 213, 214 Sex in mental evolution, 239 ff. recognition of, 219 ff. Slime molds, behavior of, 193 Spence, W., 199 Spencer, H., 24, 25, 28, 31, 50, 51, 132, 133, 139, 163, 164 Spiders, death feigning of, 200, 212, 213 Stahl, E., 97 Stentor, behavior of, 125-127 Strasburger, E., 96, 97, 98, 101 Talorchestia, death feigning of, 203, 204 phototaxis in, 57, 94 Index Temperature, influence on tro- pisms, 94, 101-103 Terns, death feigning of, 205, 206 Thigmotaxis, 103-105, 115, 182, 184, 186, 189, 215 Thomasius, 17 Thorndike, E., 33, 139-142, 144, 149-151 Torrey, H. B., 89 Towle, E. W., 104 Trial and Error, 155 ff., 254 ff. Tropisms, relation of to in- stinct, 31, 32, 52, 62, 63 reversal of, 93 Verworn, M., 99, 214 Voice, primary function of, 241-243 Voltaire, 67 Volvox, reaction to light, 99, 107, 109-111, 114 Wasmann, E., 22, 27, 121 Weismann, A., 28 Whitman, C. O., 28, 41, 42, 123, Wilson, H. V., 194 Wundt, W., 28, 122 Yerkes, R. M., 33, 104, 129 Zur Strassen, H., 195