12 AMMALS. 



eyes, and tlicsc arc wantinp; in some species. It is subdi- 

 vidcil into six classes, as follows: 



1 . Cephalapo'da. — The cuttle-fish tribe. 



2. Pterapo'da. — The tribe characterized by baving broad, 

 ilrshy, winir-like appendages in front, or organs of motion. 

 They are all oceanic species. 



3. Gasteropo'da, — A tribe wbich crawl upon a fleshy disc 

 on the under side of their bodies. Some of them form 

 shells, while others arc destitute of them, — as the slug, 

 snail, etc. 



4. Conchifera. — Acephalous shell-bearing mollusks, as the 

 oyster. 



5. Tunica'ta. — Acephalous mollusks protected by a leather- 

 like tunic, and without organs of locomotion. 



G. Polyzo'a. — Compound molluscous animals, the nervous 

 sy.stem of which consists of a single ganglion, situated be- 

 tween the mouth and anus. They have a distinct mouth, 

 surrounded by a row of ciliated tentacles, and are commonly 

 hermaphrodite and propagated by buds or ova. In the 

 mature state they are mostly fixed, though some have the 

 ]>n\ver of locomotion. 

 Hadiata. — The fourth division consists of invertebrate animals, 

 chiefly marine, whose bodily organs are arranged in a radi- 

 ate manner around the digestive cavity, and is subdivided 

 into three clas.ses, viz. : 



1. Echinoder'mata. — Invertebrate radiated animals having 

 bodies jirotected by a crustaceous covering, as the star-fish, 

 sea-urchin, etc. 



2. Acale'phse. — A class of zoophytes, — sea-nettles, jelly-fish. 



3. Polypif era. — Coral-forming animals. 



Protozoa. — A terra applied to the lowest forms of animal life, 



— animals without definite symmetry or plan of growth ; 



animalcules, sponges, etc. 

 Actinorogy (Gr. akfis, a ray, and logos, a discourse). — The 



siienee of radiated animals. 

 Amphib'ia (dr. ampJn] both or about, and hios, life). — A class 



of animals so formed as to live on land and for a long 



time under water. 

 Amphibiology {amphibia and logos). — The history and de- 



si ription of ampldbioiiR animals. 

 Cetology ((Jr. Ay/o.s, a whale, and logfis, a discourse). — The 



doctrine or natural history of cetaceous animals. 



