Walter M. Coleman

“ The habit of going to white flowers is transmitted in the structure of the nervous system; so we say that moths have an instinct to go to white objects; it is sometimes more obscurely expressed by saying they are attracted or drawn thereby.
Instincts are not Infallible.—They are trustworthy in only one narrow set of conditions. Now that man makes many fires and lights at night, the instinct just mentioned often causes the death of the moth. The instinct to provide for offspring is necessary to the perpetuation of all but the simplest animals. ”

“ The Development of Insects.—The growth and the moulting of the grasshopper from egg to adult has been studied. All insects do not develop exactly by this plan. Some hatch from the egg in a condition markedly different from the adult. The butterfly’s egg produces a wormlike caterpillar which has no resemblance to the butterfly. After it grows it forms an inclosing case in which it spends a quiet period of development and comes out a butterfly. This change from caterpillar to butterfly is called the metamorphosis. ”

“ Both plants and animals have certain parts called organs which have each a definite work, or function; hence animals and plants are said to be organized. For example, men and most other animals have a certain organ (the mouth) for taking in nourishment; another (the food tube) , for its digestion.
Because of its organization, each animal or plant is said to be an organism. Living things constitute the organic kingdom. Things without life and not formed by life constitute the inorganic, or mineral, kingdom. ”

“ The air bladder is developed from the food tube in the embryo fish, and is homologous with lungs in the higher vertebrates. Are their functions the same?
Fish that feed on flesh have a short intestine. Those that eat plants have a long intestine. Which kind of food is more quickly digested?
There are mucous glands in the skin of a fish which supply a secretion to facilitate movement through the water; hence a freshly caught fish, before the secretion has dried, feels very slippery.
The air bladder, although homologous to lungs, is not a breathing organ in common fishes. ”

“ The blood contains bodies corresponding to the white corpuscles of human blood, but lacks the red corpuscles and the red colour. The blood is sent even to the wings. The veins in the wings consist of horny tubes inclosing air tubes surrounded by blood spaces, and the purification of the blood takes place throughout the course of the circulation. Hence the imperfect circulation is no disadvantage. The perfect provision for supplying oxygen explains the remarkable activity of which insects are capable and their great strength, which, considering their size, is unequalled by any other animals. ”

“ Growth of the Grasshopper.—Some species hibernate in sheltered places and lay eggs in the spring, but adult species are scarce at that season. Most species lay the eggs in the fall; these withstand the cold and hatch out in the spring. Those hatched from one set of eggs sometimes stay together for a few days. They eat voraciously, and as they grow, the soft skin becomes hardened by the deposit of horny substance called chitin. This retards further growth until the insect moults, the skin first splitting above the prothorax. ”

“ Touch an antenna, a wing, a leg, and the abdomen in succession. Which seems to be the most sensitive to touch? The antennæ are for feeling. In some species of insects they also are organs of hearing and smelling.
The mouth parts of a grasshopper should be compared with the mouth parts of a beetle shown in Fig. 113, since they correspond closely. If the grasshopper is fed with a blade of fresh grass, the function of each organ may be plainly seen. It is almost impossible to understand these functions by studying a dead specimen, but a fresh specimen is much better than a dry one. ”

“ The outer layer of cells serves as a sort of skin. Since so much of the sponge is in contact with water, most of the cells do their own breathing, or absorption of oxygen and giving off of carbon dioxide. Nutriment is passed on from the surface cells to nourish the rest of the body.
Reproduction.—Egg cells and sperm-cells are produced by certain cells along the canals. The egg cell, after it is fertilized by the sperm cell, begins to divide and form new cells, some of which possess cilia. The embryo sponge passes out at an osculum. ”

“ The living substance of cells is called protoplasm. It is a stiff, gluey fluid, albuminous in its nature. Every cell has a denser spot or kernel called a nucleus, and in the nucleus is a still smaller speck called a nucleolus. Most cells are denser and tougher on the outside, and are said to have a cell wall, but many cells are naked, or without a wall. Hence the indispensable part of a cell is not the wall but the nucleus, 7and a cell may be defined as a bit of protoplasm containing a nucleus. This definition includes naked cells as well as cells with walls. ”

“ The bones are hollow and very thin. The large tail quills are used by the bird only in guiding its flight up and down, or balancing on a limb. The feet also aid a flying bird in balancing. The wing is so constructed as to present to the air a remarkably large surface compared with the small bony support in the wing skeleton. Are tubes ever resorted to by human architects when lightness combined with strength is desired? Which quills in the wing serve to lengthen it? (Fig. 296.) To broaden it? Is flight more difficult for a bird or for a butterfly? ”

“ Reproduction.—Do you see any swellings upon the side of the hydra? (Fig. 34, A.) If the swelling is near the tentacles, it is a spermary; if near the base, it is an ovary. A sperm coalesces with or fertilizes the ovum after the ovum is exposed by the breaking of the ovary wall. Sometimes the sperm from one hydra unites with the ovum of another hydra. This is called cross-fertilization. The same term is applied to the process in plants when the male element, developed in the pollen of the flower, unites with the female element of the ovule of the flower on another plant. ”

“ At intervals the air is forced through the glottis into the lungs. After a short time it is expelled from the lungs by the muscular abdominal walls, which press upon the abdominal organs, and so upon the lungs. Immediately the air is forced back into the lungs, so that they are kept filled. In some species the lungs regularly expand at every second contraction of the throat. This is shown by a slight outward motion at the sides. Does the motion of the throat cease when the frog is under water? ”

“ Hence they are all placed in a more inclusive division of animals, the class called mammals.
All mammals have the skeleton, or support of the body, on the inside, the axis of which is called the vertebral column. This feature also belongs to the classes of reptiles, amphibians, and fishes. It is therefore consistent to unite these classes by a general idea or conception into a great branch of animals called the vertebrates.
Returning from the general to the particular by successive steps, state the branch, class, order, family, genus, and species to which the cow belongs. ”

“ Teeth and toes are the basis for subdividing the class mammalia into orders. Although the breathing, the circulation, and the internal organs and processes are similar in all mammals, the external organs vary greatly because of the varying environments of different species. The internal structure enables us to place animals together which are essentially alike; e.g. the whale and man are both mammals, since they resemble in breathing, circulation, and multiplication of young. The external organs guide us in separating the class into orders. ”

“ Does the thigh have one bone in each? The shank of man has two bones, shin and splint bone. Do you see a groove near the end in the shank bone of a frog (Fig. 252) , indicating that it was formed by the union of a shin and a splint bone? The first two of the five bones of the ankle are elongated, giving the hind leg the appearance of having an extra joint (Fig. 253) . The foot consists of six digits, one of which, like the thumb on the fore limb, is rudimentary. The five developed toes give the five digits of the typical vertebrate foot. ”

“ Is the relative length of the joints of the leg the same in grasshoppers, beetles, etc., as in the wasp (Figs.) ? Figure 125 is a diagram of an insect’s leg cut lengthwise. The leg consists of thick-walled tubes (o, n) with their ends held together by thin, easy-wrinkling membranes which serve as joints. Thus motion is provided for at the expense of strength. When handling live insects they should never be held by the legs, as the legs come off very easily. Does the joint motion of insects most resemble the motion of hinge joints or ball-and-socket joints? ”

“ Why does the cat not need as movable a shoulder as a man? The pelvic, or hip girdle, to which the hind legs are attached, is a rigid girdle, completed above by the spinal column, to which it is immovably joined. Thus the powerful hind legs are joined to the most rigid portion of the trunk.
Mammals.—The cat belongs to the class Mammalia or mammals. The characteristics of the class are that the young are not hatched from eggs, but are born alive, and nourished with milk (hence have lips) , and the skin is covered with hair. The milk glands are situated ventrally. ”

“ The sperm cells and egg cells are poured out into the water by the adults, and the sperm cell, which, like nearly all sperm cells, has a vibratory, taillike flagellum to propel it, reaches and fertilizes the egg cell. ”

“ Tadpoles Suggestions.—Tadpoles may be studied by placing a number of frog’s eggs in a jar of water, care being taken not to place a large number of eggs in a small amount of water. When they hatch, water plants (e.g. green algæ) should be added for food. The behaviour of frogs may be best studied in a tub of water. A toad in captivity should be given a cool, moist place, and fed well. A piece of meat placed near a toad may attract flies, and the toad may be observed while catching them, but the motion is so swift as to be almost imperceptible. ”

“ The last bird has become a pest and is almost the only bird whose destruction is desirable. The female is somewhat uniformly mottled with gray and brown in fine markings. The male has a black throat with the other markings of black, brown, and white, in stronger contrast than the marking of the female. As the different species of birds are essentially alike in structural features, the directions and questions may be used with any bird at hand. When studying feathers, one or more should be provided for each pupil in the class. The feet and the bills of birds should be kept for study. ”

“ Ovipositor.—If the specimen is a female, it has an egg-placer or ovipositor, consisting of four blunt projections at the end of the abdomen (Fig. 107) . If it is a male, there are two appendages above the end of the abdomen, and smaller than the parts of the ovipositor. Females are larger and more abundant than males. In laying the eggs, the four blunt points are brought tightly together and then forced into the ground and opened (Fig. 108) . By repeating this, the grasshopper makes a pit almost as deep as the abdomen is long. The eggs are laid in the bottom of the pit. ”

“ The lungs and the gills of animals must always be kept moist. The worm cannot live long in dry air, for respiration in the skin ceases when it cannot be kept moist, and the worm smothers. Long immersion in water is injurious to it, perhaps because there is far less oxygen in water than in the air. ”

“ The Internal Organs, or Viscera (Figs. 304 and 305) .—The viscera (vis’se-ra) , as in most vertebrates, include the food tube and its glands; the lungs, the heart, and the larger blood vessels; the kidneys and bladder and the reproductive organs. The lower part, or gullet, is enlarged into a crop. It is largest in grain-eating birds. It is found in the V-shaped depression at the angle of the wishbone, just before the food tube enters the thorax. The food is stored and softened in the crop. From the crop the food passes at intervals into the glandular stomach. ”

“ In this stage the eggs are produced. When there is very little resemblance between the larva and the imago, and no pupal stage, the metamorphosis, or change, is said to be complete. When, as with the grasshopper, no very marked change takes place between the larva and the imago, there being no pupal stage, the metamorphosis is said to be incomplete. By studying the illustrations and specimens, and by thinking of your past observations of insects, determine which of the insects in the following list have a complete metamorphosis: beetle, house fly, grasshopper, butterfly, cricket, wasp. ”

“ The hydra has more active motion than locomotion. It seldom moves from its place, but its tentacles are constantly bending, straightening, contracting, and expanding. The body is also usually in motion, bending from one side to another. When the tentacles approach the mouth with captured prey, the mouth (invisible without a hand lens) opens widely, showing five lobes or lips, and the booty is soon tucked within. A hydra can swallow an animal larger in diameter than itself.
The endoderm cells have amœboid motion, that is, they extend pseudopods. ”

“ Fig. 385.—Horse, descended from a small wild species still found in Western Asia.
Ungulates, as the horse, need no other protection than their great speed, which is due to lengthening the bones of the legs and rising upon the very tip of the largest toe, which, to support the weight, developed an enormous toe-nail called a hoof. The cattle, not having developed such speed as the horse, usually have horns for defence. If a calf or cow bellows with distress, all the cattle in the neighbourhood rush to the rescue. ”

“ Migration is not a blind, infallible instinct, but the route is learned and taught by the old birds to the young ones; they go in flocks to keep from losing the way (Fig. 316) ; the oldest and strongest birds guide the flocks (Fig. 317) . The birds which lose their way are young ones of the last brood, or mothers that turn aside to look for their strayed young. The adult males seldom lose their way unless scattered by a storm. Birds are sometimes caught in storms or join flocks of another species and arrive in countries unsuited for them, and perish. ”

“ As the grasshopper breathes, does each ring enlarge and diminish in size? Each ring is divided into two parts by folds. Does the upper half-ring overlap the lower half-ring, or the reverse? With magnifying glass, find a small slit, called a spiracle, or breathing hole, on each side of each ring just above the side groove (Fig. 106) . A tube leads from each spiracle. While the air is being taken in, do the two portions of the rings move farther apart? When they are brought together again, what must be the effect? In pumping the air, the abdomen may be said to work like a bellows. ”

“ The tapeworm is a flatworm which has lost most of its organs on account of its parasitic life. Its egg is picked up by an herbivorous animal when grazing. The embryo undergoes only partial development in the body of the herbivorous animal, e.g. an ox. The next stage will not develop until the beef is eaten by a carnivorous animal, to whose food canal it attaches itself and soon develops a long chain of segments called a “tape.” ”