308 



GENERAL BIOLOGY 



Fig. 19(5. 



III. 



I. Gordius aquaticus; hinder end of male. 



II. Gordius lineatus; hinder end of male. 



III. Paragordius variua ; A, hinder end of female ; B, of male 



IV. Nectonema agile; (From Pratt's "Manual" by permission 

 McClurg & Co.) 



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 1 , 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. Pilidium 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 def erens ; j, testis ; 

 k, seminal vesicle. (After Hert- 

 wig). 



The Nematomorpha (Gr. nema, thread morphe, form), is made up 

 of the single family Gordiidae (Fig. 196). These are the common horse- 



