Lessons in ara.be ( Oilman niroal Forms England Pub- Go ^ UCSB LIBRARY &,,, . ^ LESSONS IN ZOOLOGY. COMMON ANIMAL FORMS BY CLARABEL OILMAN THIRD EDITION, REVISED. BOSTON AND CHICAGO NEW ENGLAND PUBLISHING COMPANY 1898 COPYRIGHT, 1892, BY CLARABEL OILMAN. PREFACE. This little book is the outcome of ten years' experience in teaching elementary science. It embodies the outlines of what I have found it wise to attempt with children, and is offered to teachers with the hope that it may prove suggestive and helpful. A special effort has been made to remove stumbling-blocks, by explaining points of structure that are likely to be puzzling, by giving minute directions for procuring and handling specimens, and by providing simple outline drawings that can be quickly copied upon the blackboard by one who has little artistic talent. In general, the lessons are composed of two parts, one in coarse type, consisting of short, clear statements of children's observations, frequently in their own words, with the facts that a teacher must sometimes supply in order to make a lesson complete in essential points ; the other in finer type, containing directions for the teacher and additional facts, many of which the older children can be led to discover for themselves. In some of the lessons full illustrations have been given of the method of guiding pupils' observations by questions, which it has not been thought necessary to repeat in the study of every type, though the plan remains the same in all. If ii Preface. children are carefully taught to observe, describe, and compare in the manner outlined here, it is believed that they will have a good foundation either for the later scientific study of zoology, or for the intelligent observation of animal forms in nature. I desire now to express my grpat indebtedness to Prof. Alpheus Hyatt and Messrs. D. C. Heath & Co. for the use of a large number of figures from the admirable series of " Science Guides " published by the latter. Their generosity has alone rendered it possible to illustrate the book so fully, especially in the lessons on insects. The remainder of the cuts have been drawn from various sources. CLARABEL OILMAN. Nay 14, 1892. CONTENTS PAGE THE SPONGE, - 5 HYDRA, - 11 SEA-ANEMONE, - 15 CORALS, - - - 18 STAB-FISH, - - 26 SEA UKCHIN, - - - 33 CLAM - - - - 41 OYSTER, - - - - - 48 SNAIL, - - - 54 EARTHWORM, - 56 LOBSTER, - 61 CBAYFISH AND CRAB, - ... 69 HERMIT CBAB, - - - 72 BEACH-FLEA, ... .75 SPIDER, - - 78 GRASSHOPPER, CRICKET, BEETLE, . - 92 DRAGON FLY, - - 96 BUG, W CICADA, FLY, 106 BUTTERFLY, MOTH, I 13 BEE, - - - H9 ANT, 126 AWARD FROM WORLD'S FAIR COMMISSION. Lessons in Zoology received a diploma and bronze medal from the World's Fair Commission. The award reads as follows: AWARD. "For a successful presentation of the subject in a manner suited to the comprehension of a child. The explanations and instructions as to handling specimens are such as would lead a beginner to lay a good foundation for future scientific study. The illustrations are simple and profuse, and can be reproduced on the LESSONS IN ZOOLOGY. THE SPONGE. LESSON I. For the teacher, a bath sponge with one or two large openings on the top ; for each child, a straight wire hairpin and a slate sponge, are the things needful for this lesson. Each sponge may be cnt vertically, almost to the base, through one of the large tubes, or vertical sections may be used with the whole sponges. The day before the lesson, each child should wash out his sponge and notice how it is changed by the water. Sponges should always be moist when studied. The hairpins are straightened out for use as probes. The children have already learned the following things : The hard, dry sponges took in water through all the little holes, and became soft and elastic. They are made of threads called fibres, whose ends project in little brush- like bundles on every side but one, and this side is darker and smoother than the others. There are many small holes in the sponge, and only a few large ones, or some- times only one. One or two bright pupils notice that there are holes all through the sponge, and a large tube running straight down from the large opening. Children will give some of these points spontaneously; others must be brought out by skillful questioning. Now, being careful not to tear the fibres, we put the probes into the large openings, and trace the tubes (Fig. 1, a) into which they lead, almost to the base of the 6 Lessons in Zoology. sponge. We put the probes into the small holes, and find small tubes (Fig. 1, b) leading from some of them to the large tubes ; from others, cross -tubes (Fig. 1, c) FIG. 1. Vertical section of glove sponge from Nassau, shown with the flesh. connecting one small tube with another. Some of these connecting tubes iu process of formation show plainly as channels on the surface, only partly covered in as yet by little bridges of fibres. Besides these tubes, there are others so small that we cannot trace them out (Fig. 1, d) passing in every direction through the mass of fibres. A abort talk about the home of the sponges ends the lesson. The Sponge. 1 Let us find Key West and Nassau on the map. These are the two principal markets for American sponges, which live in the Caribbean Sea and off the Florida coast. If we should visit Nassau, a boatman would take us out to the sponge fisheries. The water is very clear, and with a water- glass a tube, or box, with a pane of glass at one end which we press against the surface, we can see the bottom. Here and there on the coral rock, and contrasting with the brightly colored fishes and the brilliant hues of the sea-fans, are some dark masses fixed to the reef and sending out little jets of water from openings in the top. These are the sponges. We have in the boat a very long-handled fork, with three prongs, curved so that they will take a firm hold of the sponge, and with this our boatman pulls one off from the rock. Sometimes they are taken in a dredge, but the best sponges are brought up by divers. Our living sponge has a dark brownish or purplish flesh that covers all the fibres. After the sponges are killed by being ex- posed to the air for a day, they are thrown into pens made of stakes driven in shallow water, and left till the flesh decays. Then they are washed and trimmed, and sorted according to size, and afterward packed in bales and sent to New York or London to market. This ia true of American sponges. Mediterranean sponges, which are much finer and more expensive, receive more careful treatment. LESSON II. For this lesson every kind of sponge that the teacher can secure will be useful. Review of Lesson I. : The sponge is a mass of elastic fibres. The edges of the fibres stand out on every tide bat one, which is smooth and dark. The sponge is full of tubes that open on the outside. There are four sets of tubes : large tubes, small tubes that lead from the surface to the large ones, cross tubes that connect these 8 Lessons in Zoology. small tabes with one another, and microscopic tabes too small to be traced oat. Oar sponges come from the Caribbean Sea or the Florida coast, and were taken from the rocks with a curved fork or a dredge. Mediterranean sponges are brought up by divers. When alive they were covered with a dark colored flash, but the flesh has been removed, and only the fibres are left. OUTLINE OF NEW WORK. What was the use of the fibres ? Not only to support the flesh, but also to protect the animal. They are made of a horny substance, and so tough that fishes very seldom FIG. 2. try to eat a sponge. The hard parts of a body, support- ing and protecting softer ones, are the skeleton. We have only the skeleton of our sponges. Which side was fixed to the rock ? We are sure it was the smooth, dark side, because it appears to have been cut, and also because some of the sponges have bits of rock caught in the fibres on thin side. Where does the sponge get its food ? From the water The Sponge. 9 it takes in through the tubes. It takes in water through the small tubes that we see, and the tiny ones that we cannot trace carry it all over the sponge. When the sponge has taken from the water the very smallest plants and animals, which are its food, and has given carbonic acid in exchange for oxygen, then the water passes out through the large tubes. But as only the most minute plants and animals can pass through the microscopic tubes without danger of choking them up, a thin, porous skin FIG. 3. FIG. 4. FIG. 5. like a delicate sieve covers the whole sponge except the two or three large openings. But why does no water enter at these ? Because there is always a current flowing out from them. ID little sacs (Fig 2*) all over the sponge are cells (a) bearing each a microscopic whip (c), always lashing the water and producing the currents that carry the foul water out through the large tubes as fresh stream* come in through the small ones. In these cells, too, the food is digested. Though the outward current keeps the large tubes open, yet if a living sponge is disturbed, it will contract so forcibly as to close even these openings. * Figs. 2 3, and 4 are highly magnified, while Fig. 5 is much reduced from the natural size. 10 Lessons in Zoology. Baby sponges can swim about in the water, but they soon form a sucker at one end, by which they fix them- selves (Fig. 3) to rocks, sheila, or even the sea fans and other branching corals, and after that they never leave their home unless something tears them off. Many sponges grow on our New England coast, but are too brittle to be of any use. A little white sponge that grows among shells in the mud just below low-water mark, consists of small branching tubes about an inch long. It has no fibres in its skeleton, but everywhere in its flesh are little three armed bits of lime called spicules (Fig. 4). The common finger-sponge (Fig. 5) grows in large masses on rocks and piles. The dark red and soft yellow masses found in salt water, and the white flattened cakes often cast up on the shore and dried hard in the sun, are all sponges, the last named called by the sailors " seamen's biscuit." In a quantity of oyster shells there will usually be one or two, at least, that have been attacked by the boring sponge, which tunnels them through and through, and fin r /y destroys them by dissolving out all their lime. THE HYDRA. A tiny green or light brown jelly-like lamp as large aa the head of a small pin ; a slender stem, perhaps one fourth of an inch long, with several transparent threads waving from its tip ; or a gracefnl vase vpi'ch a few blunt projections from the top ; any cr all of these clinging to water-plants or any other support in fresh-water ponds or quiet streams, may be the hydra we are seeking. We tell the children we are going to look for a new animal, and invite some of the older ones to join na in a walk, thus enlisting their interest in the hydra in advance. It is a wise precaution to fill our glass jars at several different ponds, rather than to fill several jars from one pond, because the fact that hjdras have been found in a given place one year seems to be no guarantee whatever that they will be found there the next year. After the water has settled, the hydras will expand and many of them will collect on the sides of the jar. A dozen watch-crystals filled with pond-water, each with a bit of duckweed or some other green water-plant, make excellent ponds for as many hydras, in which children can examine them with magni- fiers, watch them eat, and observe the different shapes they assume. Pupils that are old enough will enjoy making a series of drawings showing these different form". Four questions may be put upon the blackboard, one at a time, for the children to answer from their own ob- servations : What is a hydra ? Where does it live ? What can it do ? How do new hydras grow ? After a few days the answers to these questions will bring out many of the following facts, in addition to those already mentioned. The hydra is a green or brown tube, attached by its lower end to some support, and sending out several ten- tacles near its upper end. Fig. 1 shows one magnified many times, hanging mouth downward, from a bit of wood. The upper end of the tube beyond the tentacles is called the proboscis. At the end of the proboscis is 12 Lessons in Zoology. the mouth, an opening leading into the central hollow or stomach. The tentacles are hollow, like so many glove fingers pushing out around the mouth. They are the hydra's fish- ing rods, bearing numbers of little pockets, the thread- cells on their sides, in which the fishing lines are coiled up. Each line, instead of a hook at the end of it, has three poisoned darts just where it issues from the pocket. Fia. i. FIG 2. FIG. 3. Fig. 2 represents a portion of a tentacle highly magnified, with the thread-cells in clusters on its surface. Fig. 3 is a single cell after it has burst and the thread uncoiled. When a tentacle touches a tiny worm or crustacean, the pockets burst, and the lines entangle the prey in their coils, while the poisoned darts quickly paralyze it. If some creature too large to be paralyzed is caught by the lines, then ensues a grand " tug of war " between that and the hydra. I once watched such a struggle between a hydra and the larva of an insect, which lasted an hoar and three qnartera. Even then the result was doubtful, bnt unfortunately the dish containing the com- The Hydra. 1,5 batants had to be moved, and the stirring of the water shook the ezbanated animals free from each other. The hydra is extremely sensitive, and contracts at once if touched. The variety of shapes it can assume, espe- cially when digesting its food, is very wonderful. FIG. 4-6. There are buds on some of the hydras, which at first look like knobs, then grow larger, form tentacles (Fig. 4 6), and gradually pinch themselves off from the parent, and set up for themselves. In the autumn eggs are produced (Fig. 1 a), which live through the winter. FIG. 7-n. In 1744, Trembley, a watchmaker of Geneva, performed a remarkable series of experiments upon hydras. He found that they can move about by turning somersaults (Figs. 7-11) ; that if cut in small slices, each slice becomes 14 Lessons in Zoology. a complete hydra ; that if slit in various ways, a whole colony may be produced from one (Figs. 12-13) ; and when one is turned inside out, it goes on eating, and ap- pears to enjoy life quite as much as before. FIG. 12. FIG, 13. In tide-pools and on the seaweed along our coast we find grace- ful, delicate, flower-like clusters, often mistaken for sea-mosses. These are hydroids, or hydra-like animals, whose bnds remain con- nected and form colonies. THE SEA- ANEMONE. With living anemones this lesson can be made intensely interest- ing ; without them it should not be given to children. Those who are not too far from Boston can send jars to the superintendent of Essex Bridgp. Salem, Mass., who will fill them at a reasonable price. Young anemones can be brought as far as Boston, at least, simply packed in wet seaweed. Nowhere else on oar northern coast can snch a number or variety of anemones be seen as at Beverly Bridge. The light pink or salmon colored ones show the structure best, for Fio. J. FIG. 2. when fnlly expanded they reveal the partitions of the body-cavity beautifully through their nearly transparent walls. Fig. 1 repre- sents one fully expanded ; Fig. 2, only partially. Very young anemones, not more than an inch long, will show the connection with the hydra, both on account of their small size and of their having fewer tentacles than the full-grown ones. It has been my experience that large ones do not thrive in con- finement, but they can be kept for some days if but one is placed in each jar, and care is taken to keep them cool. Candy jars are best, because the wide month allows the air free access to the water. If enough sea water cannot be had to change that in the jars every Hay, it may be aerated by pouring it back and forth a number of 16 Lessons in Zoology. times in a current of air. Young anemones may sometimes be iu- dnced to eat meat, drawing it into the month with their tentacles, and will generally take the little crab found in the gills of oysters, which they consider an especial dainty, but I have never been able to tempt the older ones with anything. They will not expand well unless kept in a cool, shady place, that shall at least remind them of the tide-pools where they hide under the shadow of the rocks and seaweed. If we try to handle them, as in taking them off the rocks, they contract into little solid lamps (Fig. 3), with app"- ently neither mouth nor tentacles. The children should examine them for several days, then brimr the results of their observations to the class, as was dune with the hydra. The body is hollow and cyl- inder-shaped, but very much larger and broader than that FIG. 3. FIG. 4. of the hydra. By the lower end it attaches itself to some object, and the upper end is a broad disk with the mouth in its center. The mouth seems to be an opening produced by folding the skin inward. Around the mouth are many rows of tentacles, which are finger-like projec- tions from the body. In the center is the stomach. Many partitions extend inward from the body-wall, some of which join the stom- ach and hold it in place, others reach only a part of the way to the stomach. They are shown like the spokes of a wheel in the cross-section given in Fig. 5, with the eggs The Sea-Anemone. 17 attached to them. In very transparent anemones it can be seen that the tentacles project over the spaces between the partitions. The stomach is not simply a cavity hol- lowed out in the body, as in the hydra, but is another hol- low bag hanging down inside the outer one. When very young the sea-anemone is like the hydra, bat as it grows, the npper end of the body-tube folds inward till ic hangs down inside as an open sac, abont half as long as the body. To illus- trate this, take a glove-finger and cat off the end to represent a hydra, then turn in the end for some distance, and the part hanging down inside will repre- sent the stomach of the anemone. The proboscis of the hydra and the stomach of the sea-anemone are therefore precisely similar in their origin, though different in their use ; that is, they are homologous. While digestion is going on, the lower end of the stomach is closed by muscles, and refuse matter is afterward ejected through the mouth. The tentacles are covered with lasso-cells, or thread- cells, similar to those of the hydra. The white threads thown out from tiny loop-holes in its sides when an anem- one is disturbed, also bear myriads of these little weapons. Sea-anemones are often produced from buds, which form around the base of the old ones. If one is torn in scraping it from the rocks, the portion left behind will become a perfect animal. FIG. 5. CORALS. LESSON I. A single large specimen of Galaxea (Fig. 1) or some other coral with large tabes, will furnish every child in a class with a tube for study, while the teacher should have a piece consisting of three or four tubes, and if possible, one or two smaller ones just budding out. Though Galaxea is best, still no teacher need omit the lesson, if she can obtain pieces of the common madrepore or finger-coral (Fig. 2). But if this is used, each child should have the end of a branch showing the large polyp at the tip, and a group of little ones around it. A living sea-anemone in the schoolroom will be a great help. Blackboard drawings of budding hydrs should also be kept for the lesson. FIG. l. FIG. 2. The children have become familiar with the idea of the skeleton in the sponge, so they at once see that coral is only the skeleton of the coral animal, and that each tube is made by one animal. They quickly make the follow- ing observations : It is white. It is shaped like a tube. It has lines on the outside. It has little walls on the inside. It is hard like stone. Corals. 19 The teacher tells them that this is a stony coral, with a skeleton made of lime. Then they look carefully at the top and the sides of the skeleton, to see if it will remind them of any animal they have studied, and find it is like the sea-anemone. Some pieces of Galaxea will show plainly that there are twelve stony partitions that nearly meet in the center of the tube, and twelve more that are shorter, bat the specimen* are often so broken that it is difficult to tell how many of the partitions are long and how many are short. It ia not best to have the children coint them unless the teacher knows from personal examination of the tubes that her pupils can readily see how many little walls of each sort there are. After the question, How are these tubes held together ? an examination of the teacher's large specimen shows that a stony, white, spongy substance connects them. FIG. 3. FIG. 4. Fig. 3 has been put on the blackboard, drawn wholly in red, be- cause it shows only the fleshy parts of the coral. This is not the Galaxea, bat it has the same kind of a stony skeleton, and the same arrangement of all the fleshy parts. The cbildren now de- scribe this figure. This new coral has a fleshy tube. It has a disk at the top of the tube, with the mouth in the center. It has ten- tacles around the mouth. There are little animals bud- 20 Lessons in Zoology. ding from some of the tubes. There is flesh covering the stony skeleton between the tubes. It is easy now to understand that the spongy filling be- tween the tubes of Galaxea is formed by the layer of flesh that covers it, and connects the animals. A colony of Galaxea is formed by the budding of young animals from this connecting layer, around the base of the old ones. Fig. 4 is a cross section of the body of a living coral, but does not show the stomach. It represents what we should see if we were to cut off the upper half of the tube and then look down upon what was left. For the blackboard the unshaded parts should be drawn in red, to represent flesh, and the shaded parts in white, for the stony skeleton. The children now tell what they see in this figure : There's a tube of flesh outside of the tube of stone. There are fleshy partitions and stony ones. The fleshy partitions are in pairs, and the stony ones are not. There are six pairs of long, fleshy partitions, and six pairs of short ones. There are six long stony partitions, and six short ones. There is a tube of flesh inside the stony tube, and the fleshy partitions grow out from that. The stony partitions are not formed by the fleshy ones, but grow in folds of the fleshy tube, that arise from its base between the fleshy parti- tions. LESSON II. The same specimens are needed as for the last lesson, with finger-coral besides. Review by asking what the coral has that the sea- anemone has, then what the coral has that the sea-anemone has not. This comparison will bring out from some bright child the observation, " Why, the coral is just like a little sea-anemone with a skeleton ! " This is exactly what we wish to find out, and the children will see it Corals. 21 FIG 5. more clearly if there is still a little colony of very small sea-anemones in the schoolroom. Fig. 5 is a diagram to be drawn in red and white, showing the upper half of the fleshy tube with the tentacles, and a cross-section through the calcareous tnbe with its partitions. To make it plainer, only six long and six short partitions are shown, and just as many tenta- cles, each long tentacle lying directly above a long partition, and each short tentacle above a short one. This figure not only shows the re- semblance between the coral animal and the sea-anemone, and the re- lations of the fleshy parts to the calcareous skeleton, but also the manner in which the fleshy base of the tubes (6) extends from one to another, thus binding together all the animals. It is this which forms the spongy filling of lime (c) between the tubes, and from which new tubes bud as the colony grows. A vertical section through a large piece of Oalaxea will often show that moat of the polyps die at the end of each season ; but the next season those that have lived spread out their fleshy bases and build a new spongy layer of lime over the taps of the dead tubas below. The children will have suspected by this time that the stomach, the month, and the poisoned lines on the tentar cles of the coral are like those of the sea-anemone, as is really the case. The class is now ready for the finger-coral, and the teacher may happen to have a piece that resembles a hand with fingers, thus suggesting its name. The children's observations follow : It is white and stony. It grows in branches. It has little bits of cups on the branches. It has very small tubes. The tube at the end of the branch is much larger 22 Lessons in Zoology. than the others. The large tube has partitions on the inside and on the outside too, but the little tubes are only rough. I think that is because the tubes are so small that the partitions can't grow very far. The smallest tubes of all are close to the large tube at the end of the branch. They look as if they had budded from the large tube. Some of these observations mast be drawn oat by such questions as will readily occur to any teacher. Now if a branch of the coral is broken and passed around the class for the scholars to examine the broken '-nds, while one with an eye for beauty, may see " something like lace with a star in the middle," and another only " a piece of stone with a little wheel in it " ; some one will finally discover that " the middle of the branch looks like a cross section of a tube " (Fig. 2a). In this way children can find out for them- selves that the large tube at the end of a branch, which has kept on growing year after year, is the one from which all the rest have budded. Great bushes of this coral sometimes grow to the height of sixteen feet, so we know that the parent polyp of each branch must live to a great age. The stony corals are the reef-builders, and a large part of every coral reef consists of branches of madrepore beaten and pounded by the waves into a mass of coral rock. These lessons on stony corals may well be followed by an imaginary trip to the ooral islands for a geography lesson. Corals. 23 LESSON 111. A whole sea- fan (Fig. 6) for the teacher, and small pieces for the children, with the stony corals before used, are needed for this les- son. These shonld be supplemented by a small piece of the precious red coral, and by a blackboard drawing of Fig. 7 in colon. In this red-coral the branches themselves, as well as the flesh covering them, are red, while the separate polyps are white. The name fan-coral, or sea-fan is quickly suggested as the teacher's large specimen is held up before the class, after which pupils' observations are in order : My piece of sea-fan is yellow. Mine has dark edges. Mine is made of a great many little branches, that join together in a network. I can break off something like a Lessons in Zoology. FIG. 7 yellow crust from the edges of mine, and there's a little dark brown wire left. I can see lots of little dots all over mine. They look like pin-holes. All are now interested to learn that the " yellow crust " is the flesh that connected all the animals of the colony, and the " brown wire " is the skel- eton. The flesh contains so many bits of lime that it be- comes hard when it dries, and so remains on the stems. The skeleton is horny. In order to understand what the ' pin- holes " are we must turn to the diagram of the red coral (Fig 7), which the children describe : There is red flesh between the coral animals. The coral animals are white. They have only eight tentacles. The tentacles are fringed. One of the coral animals has drawn itself back into the red flesh, and only its tentacles show. Two other coral animals have drawn themselves all back into the red flesh, and there's only a little bit of white in a round, red place to show where they were. It is now easy to see that the animals which make the Galaxea and the finger-coral could not hide so nicely in the flesh that covers the branch because the stony tubes would be in the way, and to draw the conclusion that the red coral has no separate tubes. Neither does the fan- coral animal make tubes. Skillful questions now lead the pupils to see that if the red-coral animals die, and the flesh dries, a red stem will be left with dried flesh on it, and in the flesh little holes that show where the animals were. So they know Corals. 25 that the " pin-holes " in the yellow flesh of the sea-fan are the places where the living animals were. The sea-fan and the red-coral, as well as the others studied, in- crease by budding, bat in all these, each separate colony starts from a single egg. Fio. 9. The lesson ends with a comparison of the stony corals and the sea-fan, which the children afterwards write out. Fig. 8 represents a coral like the sea-fan in structure, in which the branches do not interlace. Fig. 9 is the organ-pipe coral with its green polyps expanded above the red tubes. THE STAR -FISH. LESSON I. SPECIMENS : A dried star-fish and a single dried ray for each child, and a few large star-fishes in alcohol. The single rays should be cat open down the back and the contents removed, leav- ing only the sacs connecting with the tube-feet. The best way to prepare star-fishes dry is to put them into fresh water until their bodies become fully ronndad, then to soak in alcohol for an hour or two to harden the tissues, and finally to dry in the sun or a moder- ately hot oven. If alcohol is too expensive, they may be put into boiling water for a few minutes before drying. But the rays will drop off if they are left in the hot water too long. In this lesson, and the two following, parts are described as they appear on dried specimens. FIG. i. The Star -Fish. 27 Our new friend is called a star-fish, from its shape like a star with five points, which we call rays or arms. Its home is in the sea, on the piles of wharves, among the rocks, or on oyster and mussel beds. In summer it is often found above low-water mark in tide pools, but in winter it takes refuge in deeper water. When dried it gives us no idea of the rich colors, red, bluish, green, or brown, with which it beautifies the sea-bottom. Unlike most of the animals so far studied, it can move slowly from place to place. The children at once find the mouth, but we wish to study the back first, " the side that is rough all over.' 1 (Fig. 1.) Holding this uppermost we find the sieve, a round, coral-like spot that is red or orange when the star- fish is alive, and used to filter the water that passes in through it. The central part of the star-fish is the disk. The sieve is on one side of the disk, near the angle where two rays meet. If now a line is drawn from the sieve across the disk and through the middle of the opposite ray, there will be the same number of rays on each side of the line, that is, the star- V fish will be divided in halves. This gives as a hint of the bilateral symmetry seen more perfectly in the higher forms. The back of the star-fish is covered with knobs, " prickers," the children may say, called spines. They are short and FIG. 2. rounded at the tip, and we find by trying them on alcoholic specimens, that they do not move. Between and around the spines are little things looking like tiny grains of meal, which are two-pronged forks, or pedicellariae (Fig. 2), always opening and shutting. We do not know their use, unless it is to keep dirt from cling- ing to the star-fish. On alcoholic specimens these will 28 Lessons in Zoology. show beautifully in little circles around the spines. Covering the star-fish we see the brown skin, and look- ing on the inside of the back of the separate rays, we find the beams of the skeleton, like little bones imbed- ded in the flesh, making an irregular net- work. Every one who has seen a living star-fish, has noticed the difference between its rounded outline in the water and ita flat- tened appearance when thrown np on the beach. This is becanse the skin of the back is pushed oat into numerous tabes like tiny glove-fingers (Fig. 3, d), FO thin and delicate that they fill with water and again allow it to ooze oat of them when exposed to the air. These tabes, that can scarcely be seen by the naked ej e, . are really also a rudimentary sort of gills, for through their thin walls oxygen passes from the water into the body of the star-fish. LESSON II. We now study the under or month side of the star-fish. Some of the specimens will show the mouth as a large circular opening with a membrane surrounding it ; others will have a brown mass, the dried stomach, filling the opening or protruding from it ; and still others may have it nearly hidden by ten long spines, two from each ray, meeting over it like so many teeth. The mouth with the long spines around it, the stomach usually seen just inside it, and the brown suckers filling the grooves in the rays (Fig. 4) first attract our attention. The stomach can be protruded by means of muscles at- tached to it. This is because our friend feeds on shell- fish, working great havoc on the oyster and mussel beds. It clasps an oyster with its rays, then turns out its stom- ach, and proceeds to digest its victim at its leisure. A star-fish will clean a shell in this way more perfectly than it can be done by hand. The Star -Fish. 29 The four rows of suckers in each ray are on the ends of the tube-feet. In alcoholic specimens these completely fill the grooves, and in life they even extend beyond. The star-fish moves about very slowly, stretching out one ray as far as possible in front, plant- ing a few suckers at a time, drawing the body up to them, then lifting them and tak- ing a fresh start. The tube-feet at the tip of each ray are extended in front as feelers. T'i- sieve on the back connects by a tube with linn iu its walls, hence called the atone canal, with a ciioalar canal around the month, from which a tube extends down each ray. From these radial tabes branches lead to each one of the small, muscu- lar sacs (Fig. 3,