M LAW OF iniij:kitancp:; THE PHILOSOPHY OF BREEDING. " Still, through her motcB and masses draw Electric thrills and ties of law, "Which bind the strength of nature-1' — Emerson. By E . LEWIS S T U R T E V A N T , M . 1) Waushakum Farm, South Framingham, Mass. [From the •22d Annual Report of the Secretary of the Massachusetts State Board of Agriculture.] BOSTON : WRIGHT & I^OTTER, STATE PRINTERS. 79 Milk Street (corner of Federal). 1875. THE LAW OF INHERITANCE; THE PHILOSOPHY OF BREEDING. ' Still, through her motes and masses draw Electric thrills and ties of law, Which bind the strength of nature." — Emerson. ,»'" By e6''lEWI8 STURTEVANT, M.D., Waushakum Farm, South Framingham, Mass. [From the 22d Annual Report of the Secretary of the Massachusetts State Board of Agriculture.] BOSTON : WRIGHT & POTTER, STATE PRINTERS, 79 Milk Street (corner of Federal). 1875. J THE LAW OF INHERITANCE; OK, THE PHILOSOPHY OF BREEDIXG. It is now nearly three years since I made my first attempt to write a work on tlie breeding of domestic animals. I had collected a considerable mass of information, chiefly so-called facts, and it seemed an easy matter to bring these into shape for the illustration of principles which could be enunciated as laws. I soon, however, realized the difficulty of usino- this material to produce an harmonious result, as the groupino- was not only arbitrary, but the laws which they w^ere intended to illustrate were but empirical formulae, whose mutual connec- tions could not be shown. I therefore determined to seek, through further study, a solution for my difficulties ; and I may here say that my realization of the importance of force as fashioning the phenomena of vitality came entirely from a series of inductions. The facts were grouped under laws which seemed to formulate the conditions nnder which they occurred, and these laws, in turn considered as unities, pointed unmistakably to a superior law, which in its turn influenced their occurrence, — the law of persistence of force. This brief paper is not presented in order to prove a theory, but as an outgrowth arising from the supposed recognition of a cause. The cell was taken as the groundwork of my scheme, for microscopic study had ftimiliarized me with these unities of vitalized structure, and belief in a reign of law had led me to 2 The Laio of Inheritance ; or, a firm conviction that the working of natural law was univer- sal ; and if completed structure was governed by any power, then the individual parts of that structure must be influenced by the same ruling. Hence the search after truth must be from the simple to the complex, rather than the reverse. Every chauge of matter must be produced or caused by some previous coudition, for every effect must have its cause. This which accomplishes is called a force, and the change is the measure and exponent of the force used. Force is, therefore, a conception of a real existence, which, although unseen to our eyes, and not cognizable to our senses, can be studied from its effecfs, for these are seen and recognized, and may be grouped ; they can in turn be converted into the unseen, and again be reconverted into the seen, and, through modern science, so measured and accounted for, that it may be said with certainty, forces are indestructible. Forces are also strictly subject to the law of quantity. A given quantity of one force can produce a definite quantity of another. The conversion of a force may change its apparent character, and the phenomena produced by the two forms may be Avidely different. This is illustrated in heat and motion, electricity and magnetism, animal and vegetable life. Like causes produce like effects when acting in a similar manner on similar material. We know that forces may be represented by forms, aud that difference of form will indi- cate a difljcrence in the construction of the force. Force is the agent which produces changes. It has, as a conception, a numerical value and a direction of action. It can, therefore, be increased or diminished, and its direction may be interfered with or antagonized by other force. The concrete force is the equilibrium of all these opposing forces. Any change must be produced l)y an equivalent change in the force which is represented by the object undergoing change. This work is but applying the doctrine of persistence of force to vitality, as it has already been applied to ph^'sics. The forces governing vitality, chemistry and physics, must needs be but forms of the same force. Nature seems to work always under law, and her phenomena, in successive group- The Philosophy of Breeding. 3 ings, continually point to governing laws, and these in turn to others, until we must conceive of one great final law, in infinity, to which all others are subordinate. INTRODUCTORY. In the higher classes of animals our first knowledo^e of the individual life is of the union of two germs, — the one fur- nished by the female, the other by the male. The product of this union is a determinate one, and is influenced in a varied degree by multitudinous causes, the more proximate of which are parentage and environment, and the more remote the antecedents of the individual and the race. The creation of the individual and the fixing of a type for a domestic breed is, under law, largely within the power of man, and the understanding of the action and reaction of law on law, in the production of certain ends of animal structure and function, constitutes the science of breeding. The science of breeding is not necessarily an exact science. It deals with concrete phenomena, and its predictions must be, in the main, general. By acting in conformity with its predictions, the probabilities of the successful attainment of our ends in the individual is very largely increased ; when individual knowledge of the laws of causation is understand- ingly applied to the problem of breeding certain results from an animal of known antecedents, the probabilities of the posi- tion have a near approach to certainties. The scientific breeder is one who applies the laws governing the art with an understanding of the reasons upon which his expectations are based ; while the practical breeder is one who follows rules established by experiment and belief for the government of produce and production. It is as the art of breeding is united with the science that the best results may be expected ; and practice is dependent on science for its correctness and the enlargement of its usefulness. To the believer in causation — a principle which underlies the practise of all science — the animal structure and func- tion is a result produced by, and in conformity to, law ; and were the whole history of all the forces which have taken part in the production of individual animals so laid out before a 4 The Laiv of Inheritance ; or, mind capable of investigating the process, and which could so estimate their various values as to project them in a mechani- cal form, a figure could be drawn in which the resultants of the forces could be represented by a line, which would inva- riably indicate the value of the concrete forces which would be the contribution of the parties to reproduction. This is to say that certainty of result would follow complete and exact knowledge, and the corollary is equally obvious, that when we have uncertainty in practice, it can be explained by the deficiency of our knowledge. To demand this complete knowledge is to demand a mind which is infinite to our present conceptions ; but it is in our power to continuously encroach upon the borders of our igno- rance, and, while extending the boundaries of our knowledge, gain increased control over the forces of nature. The study of physics, or philosophy applied to nature, to me, at least, indicates the possibility of "spontaneous* gen- eration." But as this doctrine, so reasonable in itself, is the subject of so much prejudice, and not as yet satisfactorily demonstrated, we may at present claim that life is always derived from preexisting life. The terms which we apply to this derivative process are reproduction and generation. The word reproduction is general in its meaning, and includes the history of the changes which take place in the organs and functions of the individual, by means of which new matter is formed, as well as the production, growth and development of the new germs which make their appearance through gen- eration. The word generation, strictly speaking, has refer- ence only to the changes immediately following the act of begetting, but usually includes somewhat of the past history of the separate cells which take part in this process, as well as some history of the development of the new life thus formed. The generative process appears to consist essen- tially in the union of the contents of two cells, or the difi*er- entiated product of one cell, by which the germ of what may * Spontaneous : I use the word in the sense of produced without any special cause or method beinp assigned, as of the appearances of life without any evidence of its being produced from an existing vitality, — that is, the convertibility of forces. To use the word as if it involved the production of life without cause, or not in accord- ance with law, would involve an absurdity of thought. Tlie JPliiloso'pliy of Breeding. 5 become an iuclependent life is the result. Development is the sequel to generation. The reproductive process in itself consists in the formation of certain cells from preceding cells through well-defined procedure. It may be by subdivision, by gemmation, or through the intervening act of generation. When, by sub- division or by gemmation, each act of development appears to diminish the germinal capacity ; when, by generation, the germinal capacity appears to be renewed. By subdivision is meant the method of multiplication of cells, which, for a time, may retain their juxtaposition ; by gemmation, the forma- tion of cells which are to be cast forth, the commencement of a separate existence. The reproductive process includes the repair of injuries and the increase and renewal of parts. Growth may be the sequel to reproduction. Life may be said to commence with the cell, for it is only at this stage that we ordinarily recognize individuality. In the higher animal structures, as in the mammalia, we have the whole structure either built of or derived from cells, pre- senting a most varied and complex appearance as viewed in their completed state, but which, when studied with reference to their history and development, are seen to be all derived from this same formative element. Each cell is or has been at some time, within certain limits, an individual and inde- pendent whole, in which the vital processes are or have been repeated ; as in one, so in all. Although presenting this apparent individuality, yet, in the animal structure, these separate units are all combined, each with all, to form the harmonious whole, — the animal life. The study of the cell is the foundation from which the science of breeding is to be built up, for natural law is univer- sal and simple and unvarying, acting on all alike, but its actions disguised by environment. That the law may be seen in its primal ftu'ce, it is necessary that its workings should be sought for amid the simplest conditions and amongst the least complexity of structure. THE CELL. The cell proper, or the ideal cell, is a homogeneous and extremely simple structure, which may be defined as merely 6 The Law of Inheritance ; ovy substance within an enveloping membrane. Within a cell we usually expect to find a nucleus, or, possibly, within the nucleus another cell, which we call a nucleolus. These inner cells are almost invariably of a round or oval form, offer greater resistance to the action of chemical assents than do the exter- nal parts, and are those parts which are the most constantly found unchanged. The nucleus seems less connected with the function and specific ofiice of the cell, according to Virchow, than with its maintenance and multiplication as a living part. For the existence of the cellular element, such as we are to consider, two things are requisite, — the membrane and the nucleus. The contents change according to position and function. With these two formsj — the membrane and the nucleus, — we are enabled to examine critically the basis of some of the phenomena attending life. In the embryonic state we can readily detect the time when the whole structure is composed of cells, and as we pass onward towards birth, we see these cells changing their form and function, becoming differentiated as it were, in an increas- ing ratio with the age. The cells multiply, change their form and their function, which necessarily involves their contents, until in the grown individual it is difficult to trace the connec- tion between these elements in the various parts. The cells change, but while the activity of the cell remains, the nucleus can usually be detected. The muscle-cells become elongated and become filled with contractile matter, and capable of transmitting force ; the nucleus remains attached somewhere to this cell and is unchanged. So with the nerve-cells ; the contents differ from the muscle-cells, and it is but the nucleus which remains to indicate the kinship. We also find changes going on in the shapes of cells by outgrowths, by division, by absorption, and even by secretion and growth. These cells containing )uiclei are, in fact, individual units of a living organism, and themselves containing life and undergoing vital processes, go to make up the concrete life we recognize in the formed animal. As the processes which these vital unities pass through are all allied, we can consider some of the laws of reproduction, as derived from the study of the simple or ideal cell, leaving oui' The Philosophy of Breeding. 7 considerations concerning generation until we shall trace the union of the sperm and germ cells, and are prepared to study the development resulting therefrom. We can the better proceed in this course, if it is continually borne in mind that the cell is in a certain sense an independent being, and rules arbitrarily over certain surrounding limits. In some tissues, where there are intercellular substances, each cell rules, as pathological investigation shows, over its own defined terri- tory. In other tissues in which the cells are contiguous, each cell can run its own course without the fate of the cell lying next to it being necessarily linked with its own. In a third tissue we find the cell-elements more intimately connected with each other ; as, for instance, a stellate-cell may anasto- mose with a similar one, and in this way a reticular arrange- ment may be produced similar to that seen in capillary -vessels and other analogous structures. Yet even in this chain-work of cells, individual cells, in consequence of certain internal or external influences, undergo certain changes confined to their oavu limits, and not necessaril}^ participated in by cells adjoining. ( Virchoiv. ) Each cell in its development 7'eproduces itself. — The manner of the development need not concern us in this place. Although primarily the ideal cells are in form alike, yet through the differentiation arising from complexity of struc- ture, we see existing cells of apparently widely different origin. We have, for instance, the hepatic-cell, columnar epithelium, cells of connective tissue, muscle-cells, nerve- cells, etc., etc. In the animal organism there is a continual using up of tissues. The food passing into the body supplies the material for supplying the wastes, and cells absorbing their share at the necessary time reproduce or repair their form or their substance. That form of epidermic cells found in the nail produces nail-cells ; epithelial-cells, epithelium, etc. When the hand is cut the muscles unite by their own appro- priate tissue ; the skin heals in a like manner. When the nail is injured the remaining cells multiply themselves, as in growth, until the injury is more or less repaired. Remove the nail-cells, and the surrounding cells are unable to develop themselves into nail. £Jach cell in its develoj)ment is affected by its environment. — If 8 The Law of Inheritance ; or, the development takes place under circumstances that resistance is less in one direction, they may shoot out in this one direc- tion, and become elongated. This is well shown by columnar orcylindrical epithelium, or by transitional epithelium, asnamed by Heule, when the cells acquire points, jags and projections in the direction of least resistance, and in the epithelium of the skin. Making a section of the skin, we invariably find flat and closely-packed cells in the epidermis, with the cells on the innermost layer less flattened, and with nuclei. The further we advance inward the smaller do the cells become, the last of them standing in the form of little cjdindors on the surface of the papillse ; the epidermic cells being an advanced stage of growth, in process towards desqnamation, the inner layers the formative cells, as shown by the nuclei. Patho- logically, this law is illustrated by cancer-cells, which, like the corpuscles of pus, take their rise from the precxvisting cells and nuclei of the texture or or£>an in which the new sji-owth originates. The influence of environment is conclusively illustrated by the study of the development of some fnngi, whose spores are vegetable cells analogons to the animal cell. When the spores of pencillium crustacenm are scattered on a substance having the same chemical composition as that from which it was taken, a new crop of pencillium crustaceum is the result. Now, sow these spores on distilled water, and they swell up and finally bnrst, with the expulsion of a great number of minute bodies called zoospores, which finally develop into a plant which has been named leptothrix. If these same spores are put under the surfiice of a liquid rich in nitrogen, the zoospores expelled develop into a micro- coccus ; if the liquid is poor in nitrogen, a cypto-coccus is developed. If these spores are sown in milk, which is a fluid rich in nitrogen, we have a micro-coccus appearing, but as the milk sours by lactic acid being formed, the zoospores instead of pass- ing into a micro-coccus form, change to an arthro-coccus. If, again, a pencillium-spore germinates on milk just below the surface, we have another form called oidium lactis. If, again, a pencillium-spore is sown in fermented wine or The PMlosoi^lmj of Breeding. . 9 beer, wherein all the sugar has been converted into alcohol and carbonic acid, we have still another form, mycoderma acetis. Each cell appears to reproduce itself as it is at the time, and we thus have development at corresponding periods. The fitness of each portion of the body for its present requirements is in this manner secured ; and on this principle of a like inheritance can be explained the marvellous fact that each portion of the body is adapted to its cooperation with other portions of the body. Were distant progenitors as powerful in their influence on the progeny as others more near, the animal, instead of its present harmony of construction and function, would be an inharmonious mass of independent vitalities. We find, in accordance with this law, that in the embryo, parts appear which are fitted for ofiices and relations which are future. If, as appears to be the case, each cell reproduces itself, and is also in turn affected by environment, it would be in efiect a denial of the persistence of force, as Herbert Spencer observes, to expect that A can become A^, and still produce the same progeny as if it were still A. We may have, then, in a cell constant change, with a contin- ual reproduction of the original, and thus a definite point may be fixed, through inheritance from the past, for each cell to acquire those functions for which it is suited. Adaptation, therefore, comes through the influence of forces acting in the past, and its presence is not only determinate, but is explained by philosophy. As each cell reproduces itself as it is, includhig the varia- tions brought about by inheritance and otherwise, it seems reasonable to suppose that as all the body stands in relation of environment to each cell, and produces changes which, in turn, are transmitted,— cause and efiect, persistence of force, irrevocable law,— so the spermatic cell has the power of trans- mitting all the inherited variations brought about by the totality of the individual, including his past. Inherited variation or persistence of force seems a more philosophical hypothesis, nay, I will say theory, than pangenesis. In those cases of repair after injury, as is noticed by Paget, in an adult animal, when a part is reproduced after injury, it is made in conformity, not with that condition which was 2 10 The Law of Inheritance ; or, proper to it when it was first formed, or in its infantile life, but with that which is proper according to the time of life in which it is reproduced. In the reproduction of the foot or the tail of the lizard, they grow, as it were, at once into the full dimensions proper to the part, according to the age of the individual. Each cell ap2iears to he limited in its 2'>oicers of indefinite expansion, and thus some connection is constantl}^ preserved between the early embryotic cell and the future progeny. That is, as Paget well expresses it, the capacity of assuming the specific organic form cannot be communicated to an indefi- nite quantity of matter, for undoubtedly there is a consump- tion of power in each organization of new matter, and in the growth and maintenance of those parts already formed. We have thus in the primal force a natural limitation. This repro- ductive force appears stronger in the young than in the old, and it would, therefore, seem as if the formative power is more diminished by growth than by mere maintenance. But ao-ain, as our author observes, the capacity for the repair or reproduction of injured parts is much more diminished by development than by growth or maintenance of the body ; that is, much more by those transformations of parts by which they become fitted for higher offices, than by the multiplica- tion or maintenance of those that are already perfect in their kind and function. In other words, to improve a part requires more and more perfect formative power than to increase it does. Changes may originate in a cell from cessation of force. — If the cessation be final, we have destruction of form, or, as we say, dead matter. If partial, an incompleteness, or a check to the development of the new cell may result. The forces which originate a cell, and which are contained within the new cell, appear to principally afiect the devel- opment, while growth is largely from forces derived through nutrition. This law of cessation of force oftentimes obscures the presentation of other laws, especially the laws of sim- ilarity. The cell is an entity, containing within itself its peculiar forces, derived through inheritance and from its environment. The forces must be derived from somewhere, for energy can- Tlie Philosophy of Breeding, H not be created.* Life is potential —that is, endowed with energy. Its every manifestation proceeds from the ntilization of force. Inheritance is but an expression of a local fact, included in the phrase persistence or correlation, conservation or convertibility of force. It can, therefore, be studied in its relations to law. Like produces like in the cell ; for we have in the new cell but another expression of the parent cell, brought about from and through the transference of force. As every force acting on a cell must produce some effect (for cause and effect are correlative, of necessity), we needs have changes produced through environment, and the cell in which these changes are produced cannot be the same cell as it was previous t^ such changes, and can, in the line of transference of force, but reproduce itself as it is. There must needs be, then, in the cell a series of reproductions, in order to gain development. As another sequitur, we have limits to the power for repro- duction, for work can only be performed by the use of energy, and each change in a cell is an expression of workperfonned or energy used ; and when the changes demanded by environ- ment are too great for the remaining forces of the cell, and new forces cannot be assimilated from elsewhere, there must be a cessation of reproduction, and in time a destruction of form. THE SPERM. In considering the cell, we remarked upon the functions of the nucleus as tending rather to the maintenance and multi- plication of the cell, than to its specific office. In the sperm we shall have occasion to again refer to this important prov- ince of the nucleus. The semen— or the contribution of the male animal towards the generation of offspring— consists essentially of the sper- matozoa. Besides this, the product of the testicle, the ejected fluid contains the secretions of other glands, which probably serve the purposes of dilution for the fluid in which the spermatozoa move. Certain it is, from the beautiful experiments of Mr. Newport, that impregnation does not take place until the spermatozoon actually comes in contact with the ovum, and penetrates within its substance. * That is, formed from nothing,— an unthinkable proposition. 12 The Law of Inheritance ; or, The spermatozoon differs in aspect in various animals. In mail it is a perfectly clear, hyaloid, hlamentous body, in which a dilated portion called the head may be observed, from which is prolonged a tail or filament, which generally tapers to an extremity hardly visible from its tenuity. The head, or larger extremity, is flattened from side to side, and of a con- ical form, the pointed extremity being anterior. The sper- matic filament of the bull is somewhat similar, but the blunt portion of the oval is anterior, and there is a tendency to exhibit a darker anterior and a clearer posterior portion. In the rat and mouse the head or body of the filament is uusym- metrical and curved. In the common cock the heads are oblong and considerably elongated ; in the common sparrow, wavy. In the common perch the spermatozoa exhibit a rounded head ; in the river crawfish the filaments radiate from the circular head, and are numerous. When the spermatozoa have escaped from the male pas- sages their active movements commence, and, by the continu- ous vibratory or other movement of the filamentous tail, they are propelled forward. The tail alone has the power of move- ment, and it wisps al)out with an energy suflicient to move many times the weight of the spermatozoon. In the interior of the female organs of generation these movements are con- tinued for a longer period than in any other situation. In the queen bee the capacity for movement is retained for sev- eral months after they have been discharged by the drone bee ; and in the mammalia the movement may continue for several days after copulation. Leuwenhock points out that the spermatozoa of the dog will live or retain their movements for more than seven days preserved in a glass tube ; and Dr. Percy, of New York, reports a case where living spermatozoa issued from the os uteri of a female eight and a half days after the last sexual connection. In a bat that had been isolated for thirty-six hours, both the vagina and uterus were filled with spermatozoa in lively movement. Even this full development does not, in all cases, seem necessary for the fulfilment of the function of the spermatic filament. In certain animals, such as the decapod Crustacea and others, the spermatic elements are cast forth by the male, and are transferred to the organs of the female while they are The Philosophy of Breeding. 13 simple cells, which, during their subsequent life, form sper- matozoa within the passages of the female, as they would have doue within the organs in which the spermatic cells were first formed, the requisite conditions being duly supplied. We will now touch upon the history of the development of the spermatozoa, and will thus trace their kinship with the cell. In the earlier stages of physiological science they were regarded in the light of animalculaj. At the present time they are considered as epithelial cells, or, as Dr. O. W. Holmes expresses it, are related to ciliated epithelium. They are, as has been before stated, the product of the testes. The testicles are a couple of true glands, containing the secreting elements in the form of complexly convoluted tubules, — the spermatic tubes, or tubuli semeniferaj. These consist of a fibrous coat, internal to which is a basement membrane surrounded by epithelium. The character of this epithelium and the contents of these tubes vary with the age. In boys and young animals the slender tubuli contain nothing but minute, clear cells, the most external of which may be regarded as epithelial cells. The spermatozoa are not found in these tubes until puberty in man, and among some animals are only developed at certain periods. The epithelium lining the tubes is most distinct when spermatozoa are not being found, but when the function of the gland is being actively performed the tubes are seen to be entirely occupied by cells, filled with nuclei, in which the spermatozoa are ultimately developed. The method of development is thus described by Todd and Bowman: "The cells become detached from the basement membrane, increase in size, and assume a more spherical form, the contents at this time being entirely granules ; at length, however, several clearer points or nuclei are seen in the inte- rior of the cell, which is now passing down the tubule towards the vas deferens, while it is succeeded behind by the formation of new cells. The nuclei in the interior enlarge, and are often seen to contain nucleoli. The parent cell having much increased in size from the development of its nuclei into cells, appears to undergo no further change ; but in each of the contained cells, which vary much in number, one spermato- zoon is developed on the inner wall, in the form of a spiral 14 The Law of Inheritance ; or, filament, as was first described by Kolliker. The spermato- zoon escapes into the interior of the mother cell by the rupture of its development cell. Others are in like manner set free, and they arrange themselves in a parcel, which may ultimately consist of a vast number of separate spermatozoa, with all the heads arranged in one direction, and the tails in the opposite one." Professor Kolliker has arrived at the conclusion that the spermatozoa are not developed in the nuclei of the cells, but from them. The nucleus becomes of an oval form, and one extremity is elongated to form the tail. It is thus seen that the spermatozoon is a living unit which originates from Avithin the cell, and appears to be developed from the nucleus, which, as we have before stated, seems to be the one element of all cells which concerns itself with their production ; and as is shown by those cases of cells at emission being developed into the spermatic lihiment in the female passages, there is a developmental power inherent in the cell jifter it has become detached from the basement-membrane, or, in other words, has changed its appearance but little from the ordinary epithelium. The production of these cells seems to be somehow analogically allied with the process of gem- mation, as in the ideal sperm-cell and the ideal bud. We have, at first, a separation from the parent, and, secondly, ma}' have the evolving of apparatus to be used in reproduc- tion. At this point the resemblance seems to be lost, as in the spermatic element there is absolutely required, so fiir as we know, that there shall be a meeting and nnion with another cell to complete the new life, while in the gemmation process, the spore itself, as in the female, may develop itself into a structure containing organs from which the new gen- eration originates. This spermatic-cell is allied with the other cells of the body, as with the whole body it has been formed through the successive development of cells, — simple nntil after fecun- dation. It apparently is primarily an epithelial cell, and it is only as the body within which it is found attains age, or, as is probable, it is only after cell has reproduced cell for many generations, transmittina: its own likeness each time with the accumulated and accumulating variations, that the spermatic The Philosophy of Breeding. 15 filament is formed ; that is, being a hipjlily-endowecl structure, it can be formed only tlirough successive reinforcements of force, or successive developments ; that is, it must pass through the stated course of heredity with variation. Its after- functions, or, as we may express it, the inherent power locked up in these minute filaments, in man scarcely one-eight hun- dredths of an inch long, indicates high endowments, just as the power extracted from a lump of coal is the measure of the power which was made latent in the stone form in its pro- duction. This is also apparent in the close connection known to exist between the nervous system and the organs of gen- eration and the ph3^sical lassitude following their abuse. This close connection between the nervous and generative systems explains some of the problems attending the study of inher- itance. Each cell partakes, it is probable, through inheritance with variation, of the changes which have taken place, and which are taking place, both mentally and physically, in the body. It is a concretion of possibilities derived through a long course of vital changes, and which is enabled, under favorable circum- stances, to transmit its accumulated powers, through union Avith another cell, to a remote posterity. The hypothesis of pangenesis demands the presence of granules or gemmules 'which are freely circulating through the system, and which are supposed to be transmitted from the parent to the oflTspring, and which can lie dormant or become developed in the generations that succeed. To me, this is unthinkable, and I prefer to suggest that the law of persistence of force requires that no change can take place in a cell without changing the possibilities of that cell in its multiplication and future development ; that each cell is the sum of all the forces which have acted on it in the past and are acting in the present ; that the intimate connection of the generative cells with the Avhole body, arising through their high endowment, stores up in them a greater store of possibilities, brought about by their extreme complexity of environment. These possibilities may be looked upon as forces which are modified by every antagonistic force, and, strengthened by every force acting in their own direction, only require suit- able conditions to become developed or affect development, — 16 The Law of Inheritance ; or, that is, to add forces so as to be changed into other forces. In a word, inheritance is but the transmissal of forces, and inheritance can be general in respect to the whole bod}', and local in respect to the tissues and parts of the body. In the history of the development and in the formation of the spermatozoon we recognize a segregation and localization, — that is, the putting into form of forces ; and when this spermatozoon unites with another cell, — the ovum, under certain conditions, — a union of forces takes place, and, the phenomenon of individual life Ijeing thus superimposed, these forces are able to accumulate and store up the forces necessary in turn for development, growth and future transmissal. The whole form and character of the individual is the equilibrium of the forces which were united to give him birth, and those additional forces added on or influencinor durinof life. If we suppose development and growth taking place, or any of the phenomena attending vitality, without the corresponding expenditure of power, we are involved in an absurdity ; for appropriation of and transmissal of force, not its creation, is consistent with the reign of law, such as modern science recoffnizes as existing. In this place it may be well to define our understanding of force. It is a power which produces change, or acts to change any relations whatsoever between matter, — as the force of grav- ity, cohesive force, centrifugal force, vital force. Modern science has determined that forces, like matter, are indestruc- tible, and that many of them are mutually convertible, and that these mutations are rigidly subject to the laws of quantity. Every manifestation of force must needs come from a pre- existing equivalent force, and must give rise to a subsequent and equal amount of some other force. We have laws govern- ing force as we have laws governing matter. Every change involves expenditure of force. As a summary, we may look upon the spermatozoon as a cell, the representative of the organism through which it has been developed ; as one of the individual unities which are freighted with force beyond its own needs, and but requires the suited conditions of union with the proper germs under suitable circumstances, to develop that, force. Just as, for illustration, we may consider coal or water as the represent- The Philosophy of Breeding. 17 ative of the forces used in their formation. Through the destruction of their power, their forces can be liberated to again pass into other powers of energy. THE GEEM. That portion of the female organism Avhich most nearly conforms to the spermatozoon of the male, is the ovum, or ^^g, or, more accurately speaking, the most essential part of the ovum, the germinal spot. The germinal spot appears to cor- respond to the nucleus of the cell in many respects. The germinal vesicle, in which the germinal spot is contained, appears a cell surrounded by a mass of nutrient matter known as the yolk, and the whole surrounded by a vitelline membrane or yolk-sac. The ovum takes its origin from within the stroma, or the cavity of the ovaries, which answer analogically to the secret- ing process of the testicle. In many of the lower .animals the testes and ovaries bear a close resemblance to each other, and the same holds good in the early or embryotic condition of the generative apparatus of man. In some of the lower grades of animals, as generally in the articulates and mol- lusks, the ovaries have a glandular character, but in the verti- brates the ova are evolved in the midst of a solid fibrous tissue 6r stroma. The likeness between the spermatozoa and the ova is again indicated l)y the fact that they both appear to be the product of cell-action, with development having taken place after the dehiscence of the cell from its companion cells. "VVe thus have in the sperm the mother-cell containing the nuclei which are formed into ciliated cells, and which are to develop a vitality sufficient to support the motion necessary to them for the fulfilment of their uses. In the ovum we recognize an advanced development, in which the cell containing its nucleus is the essence ; the nucleus in both being the essential part for the exercise of the complete function of either, — the pro- duction of the individual life. The ova in women originate in ovisacs or follicles, usually termed Graffian vesicles, which are imbedded in the more peripheral portions of the stroma. Each follicle in its fully formed condition consists of a membrane and contents. First, 3 18 The Law of Inheritance ; or, a highly vascuhir layer which is united with the stroma of the ovary by a rather loose coimective tissue. This membrane is composed of undeveloped, nucleated, formative tissue, inter- mixed with numerous, mostly fusiform, formative cells. Second, an epithelium lines the entire follicle, and on the side looking towards the surface of the ovary, where the ovum is situated, presents a wart-like thickening projecting towards the interior and enveloping the ovum. In this germinal eminence, as it is called, close upon the fibrous membrane of the follicle, and, therefore, in the most prominent part of it, is placed the egg (ovulum) imbedded in the cells of which the eminence is composed. In the articulated and molluscous animals generally the ovum is produced from ovaries, which have a glandular character, — those of the former retaining a vesicular type ; of the latter, often prolonged into convoluted tubes. In the ovaries of the advanced foetus and new-born child, Graftian follicles are abundant, and the ovum can be seen within them. According to Dr. Ritchie, there is a continual rupture of ovisacs and discharge of ova taking place even during childhood ; and I have myself verified this observation in the ovary of a calf but a few days old. It is only as the period of puberty is reached that the ova are perfectly developed and capable of being impregnated. The number of ova which may be produced by a single animal is immense. In fishes the number is simply incon- ceivable. The number spawned by a single cod is stated at from one to nine millions. In the herring as many as sixty- eight thousand six hundred and six ova have been counted from one fish. Among animals of the higher orders we also have an ample provision. Dr. Barry calculates that the ovary of the cow, at the period of puberty, contains as many as two hundred millions ovisacs to a cubic inch of the stroma.* In the human female the ovary may contain from thirty to one hundred follicles. In the absence of proof, it seems philosophical to suggest, that, judging from analogy, the ovum is directly the resultant of cell-action ; that cells in the stroma, through a process of reproduction, finally arrive at a stage where a certain inde- * Todd and Bowman's Physical Anatomy, p. 8i8. The Philosophy of Breeding. 19 peudence of action can be sustained, and development pro- ceeds, aided by the actions going on simultaneously in the surrounding cells, producing changes on them, and having changes produced in them in turn on themselves. The existence of and discharge of ova during childhood, and the incomplete- ness of the organization of such ova, by which impregnation is rendered impossible ; the existence of the nuclei, which suffer less change, or resist changes longer than the cell ; the formative power which the cells of the ovary appear to possess even after the extension of the ova, as Avitnessed in the corpus lecteum ; the numbers of ova beyond all seeming needs ; the appearance of the germinal vesicle first in the order of development, and the analogy between the sperm and the germ in their development, are all suggestive of this view. In the preparations for fecundation the mother-cell of the testes possesses nuclei which develop into spermatozoa and are scattered as animated particles within the secretions of the seminal tubes. In the ovum, as a preparation for fecundation, it seems probable from the observations of many skilled observers, that the germinal vesicle is dissolved (like the mother-cell), and the diffusion of its contents (which originate or are formed from the germinal spot or nucleus) through the yolk, which may be considered in some sense a secretion. Certain it is that the ovum, like the spermatozoon, repre- sents vitality. A period in its development arrives when it becomes capable, under fit conditions, of establishing an indi- vidual and independent life. This condition of vitality may remain for a considerable, though uncertain, period of itself; the ovum has reached the highest development that it is ordi- narily capable of, and it requires for its future development a set of conditions external to itself, the union of the fecundat- ing germ and fit surroundings. This ovum is, however, filled with possibilities. It con- tains, as does the sperm, elements which may go to make up an individual and independent life, and is one of the connect- ing links which unite all the vital forces of the past with future irenerations. It is a vehicle for the transmissal of the forces which have had part in its own evolution. Each cell or completed ovum contains its own forces, which 20 The Law of Inheritance ; or, cannot bo alike in each, such is the complexity of environ- ment, bnt which can approximate in likeness according as the conditions of their evolution have been more similar. We cannot expect that in the continual development of ova into new beings — although the conditions of the environment of the development brought about by fecundation may be very similar — parallel results shall in any case be obtained. In the case of brothers and sisters we usually see resemblance, never exact likeness of form or character, — occasionally an unlike - ness of form or character. In twins it is a matter of constant observation that the resembhmces are usually quite close. In the latter case, where the conditions of fecundation are alike, and the developuuent of the various germs which make the new being are somewhat cotemporaneous in the time of their development, and consequently exposed to a somewhat similar environment, such differences as we observe between the two offspring are to be largely explained by the difference in the forces which were contained in the germs. The ovum, like the sperm, being a representative of a con- crete force, which has been made up from the action and reac- tion of all acts affecting past ancestors which have had any effect on its development, it must follow, as a matter of course, that any individual act affecting the development of these cells, must likewise be represented in the modifications pro- duced in the forces which, through the ovum, are transmitted. On this view we can explain the action of imagination, or of a previous impregnation, upon the offspring. A long con- tinued or a violent impression on the nervous system through the changes following every act through which there is a con- sumption of force, would necessarily modify, in some form, the development of cells whose functions are peculiarly those of transmissal. The fact that the development of the ovum in woman is checl