2 zoozoar. 



an examination we shall obtain a fair idea of the form and 

 structure of the great class of mammalia, or mammals, of 

 which the dog and cat are examples. Moreover, we should 

 study how the animal walks, how its heart beats, or its eyes 

 see. This is studying the physiology of the animal. Then 

 we should learn how the animal grows or develops from 

 the^egg, and this is called Embryology, the germ of an ani- 

 mal being called an embryo. The bodies of animals are 

 made up of cells. A cell is a microscopic portion consist 

 ing of a jelly-like substance called protoplasm. Animal- 

 cules are composed of but a single cell; such creatures are 

 said to be unicellular, but most animals are formed of bone 

 or shell, muscles, nerves, etc. These parts are made up of 

 cells. Hence these animals are many-celled. The cells 

 form tissues, such as muscular or nervous tissue. The 

 study of cells and tissues is called Histology. Finally, we 

 should acquaint ourselves with the habits and mental traits 

 of the animal, and this is called Psychology. 



A fish is tbe most convenient vertebrate for ordinary 

 school laboratory work. The object of these lessons is to 

 induce the scholar to depend as far as possible upon the 

 use of his own eyes and brains. He should observe with care 

 some of the common animals here described, most of which 

 he can readily obtain, and then study their form, habits, 

 and the leading features of their anatomy. After examin- 

 ing a starfish, clam, lobster, insect, and fish, and reading 

 about their mode of growth, he will obtain a knowledge of 

 the principal groups of the animal kingdom which he will 

 remember throughout life. 



Classification. — There are estimated to be upwards of 

 250,000 species of animals now living on the surface of 

 the earth. How all these forms are related and how they 

 differ comprises what is called the classification of animals 

 or SYSTEMATIC ZOOLOGY. 



When Linnaeus, the father of natural history, undertook 

 to classify animals he divided the animal kingdom into 

 classes, orders, genera, and species. Thus at present all 



