Flatworms and Threadworms 



309 



ii. 



Fig. 196. 



I. Gordius aquaticus ; hinder end of male. 



II. Gordius lineatus ; hinder end of male. 



III. Paragordius varius; A, hinder end of female; 

 ,, ™ V - Nectonema agile; (From Pratt's "Manual' 

 McClurg & Co.) 



III. 



B, of male, 

 by permission 



IV. 



of A. C. 



A. B. Two species of Rotifera. A, Philodina. B, Hydatina. 

 (From Parker and Haswell, after Hudson and Gosse.) 



C. Diagram showing the anatomy of a Rotifer. a, anus; 

 br, brain; c\ preoral, and c 2 , postoral circlet of cilia; c.gl, ce- 

 ment gland; cl, cloaca; d.ep, dermic epithelium; d.f, dorsal 

 feeler; e, eye; fl.c, flame-cells; int, intestine; m, muscles; mth, 

 mouth; nph, nephridial tube; ov, ovum; ovd, oviduct; ovy, ger- 

 marium; ph, pharynx; st, stomach; vt, vitellarium. (From 

 Parker and Haswell.) 



D. Philidium larva of a Nemertine. D, alimentary canal; 

 E, E', the two pairs of ectodermal invaginations. (From 

 Sedgwick, after Metschnikoff.) 



Fig. 197. 

 The arrowworm, Sagitta hexap- 

 tera (of the group Chaetognatha), 

 ventral view, a, mouth; b, intes- 

 tine; c, anus; d, ventral ganglion; 

 e, movable bristles on the head; f, 

 spines on the head; g, ovary; h, 

 oviduct; i, vas deferens; j, testis; 

 k, seminal vesicle. (After Hert- 

 wig.) 



