10 



FIRST zmsom in zoology. 



cells are called Metazoa. The series of Metazoa* comprises 

 the seyen higher branches, i.e., the Porifera, Cmlenterata, 

 Vermes, Echinodermata, Mollusca, Arthropoda, and Ver- 

 telrata. Their relationship may be expressed by the fol- 

 lowing 



Tabulak View of the Eight Bbanches op the Antmat. Kingdom. 



Vni. Vertebrata. 

 Fishes to Man. 



VII. Arthropoda. 

 Crustaceans, Fodostomata, ATachnidans, Myijopods, and Insects. 



VI. Mollusca. 

 Clams, Snails, Cuttles. 



V. Echinodermata. 

 Crinoids, Starfish, etc. 



I 



IV. Vermes. 

 Worms. 



III. Cmlenterata. 

 Hydra, Jelly-flghes. 



II. Porifera. 

 Sponges. 



Metazoa. 

 Many^:elled animals, with 3 cell-layers. 



'I. Pbotozoa. 



Single-celled animals. 



Paleontology. — The existing animals were preceded in the 

 earth's history by multitudes which are now extinct. Their 

 remains in the shape of bones, teeth, or shells, etc., are 

 called fossils, and the study of fossil animals and plants is 

 called Paleontology. 



* In the latter group the cells are arranged in two, mostly three, fun- 

 damental cell-layers. Of these cell-layers, the outermost is called the 

 ectoderm; the middle, the mesoderm,; the innermost, the end/)defrm. 



