Vernon L. Kellogg

“ But as we learn the things that this formless viscid speck of matter does, we see that it is truly an animal; that it really does those things which we have learned are the necessary life-processes of an animal. ”

“ The members of a group resemble each other in structure because they are actually blood relations. But as their common ancestor lived ages ago, we can learn the history of this descent, and find out these blood relationships among animals only by the study of forms existing now, or through the fragmentary remains of extinct animals preserved in the rocks as fossils. As a matter of fact we usually learn of the existence of this actual blood relationship, or the fact of common ancestry among animals, by studying their structure and finding out the resemblances and differences among them. ”

“ The single-celled body.—The study of Amœba and Paramœcium has made us acquainted with an animal body very different from that of the toad or the crayfish. These extraordinarily minute animals have a body so simple in its composition, compared with the toad's, that if the toad's body be taken for the type of the animal body, Amœba might readily be thought not to be an animal at all. The body of Amœba is not composed of organs, each with a particular function or work to perform. Whatever an Amœba does is done, we may say, with its whole body. ”

“ It is evident, of course, that such a natural selection or survival of the fittest and consequent adaptation to environment presupposes differences among the individuals of a species. And this is an observed fact. No two individuals, although of the same brood, are exactly alike at birth; there always exist slight variations in structure and performance of functions. And these slight variations are the differences which determine the fate of the individual. One individual is a little larger or stronger or swifter or hardier than its mates. ”

“ The life-history of comparatively few kinds of animals is exactly known; the instincts and habits of comparatively few have been studied in any detail. The kinds of food demanded, the feeding habits, nest-building, care of the young, cunning concealment of nest and self, time of egg-laying or of producing young, duration of the immature stages and the habits and behavior of the young animals—a host, indeed, of observations on the actual life of animals, remain to be made by the "field naturalist." ”

“ When many individuals of a species live together in a community in which the different kinds of work are divided more or less distinctly among the different members and where each individual works primarily for the whole and not for himself; where there is, in other words, a thorough mutual help and mutual dependence among the members of the community accompanied by a division of labor, the life of the species is truly communal. Those animals which show the most elaborate and specialized communal life are the termites or white ants, the social bees and wasps, and the true ants. ”

“ Feeding habits, economics, and protection of birds.—The feeding habits of birds are not only interesting, but their determination decides the economic relation of birds to man, that is, whether a particular bird species is harmful or beneficial to man. Casual observation shows that birds eat worms, grains, seeds, fruits, insects. A single species often is both fruit-eating and insect-eating. Do fruits or do insects compose the chief food-supply of the species? ”

“ The facts about the bodily make-up or structure of animals constitute that part of zoology called animal anatomy or morphology; the facts about the things animals do, or the functions of animals, compose animal physiology; the facts about the development of animals from young to adult condition are the facts of animal development; the knowledge of the different kinds of animals and their relationships to each other is called systematic zoology or animal classification ”

“ Life-history.—Any animal which hatches from an egg has undergone a longer or shorter period of development within the egg-shell before hatching. The development of an animal from first germ-cell to the time it leaves the egg, for example, the development of the embryo chick from the first cell to time of hatching, is called its embryonic development; and the development from then on, for example, that of the chick to adult hen or rooster, or that of tadpole to frog, is called the post-embryonic development. ”

“ It is only in rare cases that any land-animal can independently cross a great ocean. Thus the land-animals of Australia differ from those of all other countries, and those of Africa and South America have developed almost independently of one another. The ocean is, as already mentioned, also a barrier for fresh-water aquatic animals, and even marine fishes which live normally in shallow waters along the shore rarely venture across the great depths of mid-ocean.
The obstacles or barriers met with determine the limits of a species. Each species broadens its range as far as it can. ”

“ In fact the whole work of the introduction and diffusion of valuable food-animals in territory not naturally included in the habitat of the species is based on our knowledge that the habitat of a species is often determined by physical barriers rather than by exclusive fitness of environment. Within the natural habitat the environment is fit for the species' existence, outside of it the environment may be fit. ”

“ Are all animals similarly complex in structure, and capable of doing such a great variety of things? We shall find that the answer to this question is No. There are many animals in which the body is composed of but a few parts, and whose life includes the performance of fewer functions or processes than in the case of the toad. There are many animals which have no eyes nor ears nor other organs of special sense. There are animals without legs or other special organs of locomotion; some animals have no blood and hence no heart nor arteries and veins. ”

“ The struggle for existence.—The numbers of animals are stationary because of the tremendous mortality occasioned by the constant preying on eggs and young and adults by other animals, because of strenuous and destructive climatic and meteorological conditions, and because there is not space and food for all born, not even, indeed, for all of a single species, let alone all of the hundreds of thousands of species which now inhabit the earth. There is thus constantly going on among animals a fearful struggle for existence. ”

“ Nor is hearing, nor is leaping, nor are many of the things which the toad can do; and animals can exist, and do exist, without any of those organs which enable the toad to see and hear and leap. But the body of any animal must be capable of performing the few essential processes which are necessary to animal life. How surprisingly simple such a body can be will be later discovered. But in most animals the body is a complicated object, and is able to do many things which are accessory to the really essential life-processes, and which make its life complex and elaborate. ”

“ All that is known by scientific men and others of these different kinds of facts about all the 500,000 or more kinds of living animals, constitutes our knowledge of animals and is the science zoology. ”

“ An important difference between the locomotive engine and the toad's body is that one is a lifeless machine and the other a living machine. But there is a real similarity between the two in that both are composed of special parts, each part performing a special kind of work or function, and all the parts and functions so fitted together as to form a complex machine which successfully accomplishes the work for which it is intended. ”

“ The lungs are the principal organs for the function of breathing; the heart, arteries and veins are the organs which have for their function the circulation of the blood; the principal organ concerned in the digestion of food is the alimentary canal, the function of seeing is performed by the organs of sight, the eyes, and so one might continue the catalogue of all the organs of the body and of all the functions performed by the animal. ”

“ The mammals constitute the highest group of animals, including man, the monkeys and apes, the quadrupeds, the bird-like bats and fish-like seals and whales; in all about 2500 species. They are found everywhere except on a few small South Sea islands. Only a few species, however, have a world-wide distribution. The name Mammalia is derived from the mammary or milk glands with which the females are provided and by the secretion of which the young of this class, born free in all but a few of the lowest forms, are nourished for some time after birth. ”

“ Laws of distribution.—The laws governing the distribution of animals over the earth's surface have been recently [20] expressed in a simple statement as follows: Every species of animal is found in every part of the earth unless (a) its individuals have been unable to reach this region on account of barriers of some sort; or (b) having reached it, the species is unable to maintain itself, through lack of capacity for adaptation, through severity of competition with other forms, or through destructive conditions of environment ”

“ The bee with the kind of life-history just described is a worker. It has been demonstrated that the eggs which produce workers and those which produce queens do not differ, but if the workers desire to have a queen produced they tear down two or three cells around some one cell, enlarging this latter into a large vase-shaped cell. When the larva hatches from the egg in this cell it is fed for its whole larval life with bee-jelly. From the pupa into which this larva transforms issues not a worker but a new queen. ”

“ The barnacles present several unusual conditions with regard to the internal organs. They have no heart nor any blood-vessels; most of the species are hermaphroditic; and there are other indications of a degenerate condition. This degeneration of the barnacles is due to their fixed life, the results of which are like those of a parasitic life. The young barnacles when hatched from the egg are free-swimming larvæ as with the other Crustacea. They finally attach themselves and undergo the changes, some of them of degenerative nature, which produce the body-structure of the adult. ”

“ A well-known zoologist has said: "The food-supply of marine animals consists of a few species of microscopic organisms which are inexhaustible and the only source of food for all the inhabitants of the ocean. The supply is primeval as well as inexhaustible, and all the life of the ocean has gradually taken shape in direct dependence on it." The marine Protozoa are the only animals which live independently; they alone can live or could have lived in earlier ages without depending on other animals. They must therefore be the oldest of marine animals. ”

“ In this chamber a single egg is laid, and some insects or spiders, captured and so stung by the wasps as to be paralyzed but not killed, are put in for food. The nest is then closed up by the female, and the larva hatching from the egg feeds on the enclosed helpless insects until full grown, when it pupates in the cell and the issuing adult gnaws and pushes its way out of the ground. Each species of wasp has habits peculiar to itself, making always the same kind of nest, and providing always the same kind of food. ”

“ The most poisonous snake of South Africa is the large and ugly puff-adder, which puffs itself up when irritated. An interesting group of snakes is that of the Hydrophidæ or sea-snakes, which swim on the surface of the ocean by means of their flattened and oar-like tails. These forms live in the tropical portions of the Indian and Pacific oceans, ranging as far north as the Gulf of California, and spend their whole life in the water, "out of which they appear to be blind and soon die." They are extremely venomous, but are all of small size, rarely two feet long. ”

“ When the enemy of the host crab prevails, the Sacculina goes down without a chance to struggle in its own defence. But far more important than the disadvantage in such particular or individual cases is the fact that the parasite cannot adapt itself in any considerable degree to new conditions. It has become so modified, so specialized to adapt itself to the very special conditions under which it now lives, it has gone so far in giving up organs and functions, that if present conditions change and new ones come to exist the parasite cannot adapt itself to them. ”

“ There is also a distinct circulatory system, but the "blood" which is carried by these organs and which fills the body-cavity consists mainly of sea-water, although containing a number of amœboid corpuscles containing a brown pigment. There is no organ really corresponding to the heart of the higher animals. There are distinct organs for the production of the germ or reproductive cells. The sexes are distinct (except in a few species) , each individual producing only sperm-cells or egg-cells, but the organs or glands which produce the germ-cells are very much alike in both sexes. ”

“ To collect, it is necessary to find the animals alive; one learns thus their haunts, their local distribution, and something of their habits, while by continued work one comes to know how many and what different kinds or species of each group being collected occur in the region collected over. Collecting requires the sacrifice of life, however, and this will always be kept well in mind by the humane teacher and pupil. Where one set of specimens will do, no more should be collected. ”

“ The mouse is a prolific mammal, producing from four to six times a year broods of from four to eight young. The mouse makes a cosy nest of straw, bits of paper, feathers, wool or other soft materials, and in this the young are born. The newly born mice are very small and are blind and helpless. They are odd little creatures, being naked and almost transparent. They grow rapidly, being covered with hair in a week, although not opening their eyes for about two weeks. A day or two after their eyes are open they begin to leave the nest, and hunt for food for themselves. ”

“ With a change of environing conditions, certain species are unable to maintain themselves. With the destruction of the forests going on in parts of our country the great host of wood-creatures, the bears, squirrels, the wood-birds and insects, can no longer maintain themselves, and grow rare and disappear. Man often also influences the status of a species by checking its increase either by actual slaughter, as with the bison and passenger-pigeon, or by making adverse changes in its environment, as by destroying forests, or putting the plains under cultivation. ”

“ Rapacious egg-collecting, legislation against birds wrongly thought to be harmful to grains and fruit, and the selfish wholesale killing of birds by professional and amateur hunters, help in the work of destruction. Apart from the brutality of such slaughter, and the extermination of the most beautiful and enjoyable of our animal companions, this destruction [18] works strongly against our material interests. Birds are the natural enemies of insect pests, and the destroying of the birds means the rapid increase and spread, and the enhanced destructive power of the pests. ”

“ All animals produce far more young than can survive. As a matter of fact, which we may verify by observation, the number of individuals of animals in a state of nature is, in general, about stationary. There are about as many squirrels in the forest one year as another, about as many butterflies in the field, about as many frogs in the pond. Some species increase in numbers, as for example, the rabbit in Australia, which was introduced there in 1860 and in fifteen years had become so abundant as to be a great pest. ”