14 A SYNOPSIS OF ANIMAL CLASSIFICATION. 



tine, when present, usually com- 

 plete. 



Sub-class I. NEMATODES Long, cylindrical unsegmented 



worms. Body not contractile but 

 very pliable. Two lateral excre- 

 tory canals. Intestinal canal long 

 and straight, with mouth and anus 

 generally present. Sexes usually 

 separate. Free-swimming and 

 parasitic forms. 



X Ascaris, Trichina. 



Supplementary form. Sagitta, a small marine worm with caudal and 

 lateral fins, and a paired group of bristles which serve as jaws. Is 

 assigned to a separate order — Chcetognatha. [Cf. p. 21.] 



Sub-class II. ACAKTHOCEFHALi. . . .A Single family of worms, externally 



similar to last, but with an ante- 

 rior extensile proboscis beset with 

 hooks, and no intestinal canal. 

 Larval stage in crustaceans and in- 

 sects; adult in intestine of verte- 

 brates. X Echinorhynchtcs. 



Class III. TROCHELMINTHES Vermes of various shape, never 



worm-like, and usually minute. 

 The locomotive species possess a 

 ciliated band or irochus, which, in 

 the sessile forms, is represented 

 by ciliated tentacles. 



Sub-class I. ROTIFERA Minute locomotive Trochel- 



minthes, with ciliated areas and 

 generally a few posterior segments. 



Order i. Cephalotricha True roH-fers (i.e., wheel-bearers), 



with cilia at the anterior end, 

 usually covering two protrusible 

 organs resembling wheels. 



•K Brachionus, Rotifer. 



