THE HAIR-WORMS. 



171 



The second suborder, Gordiacea or hair-worms, differ in 

 their mode of development from the true Nematode worms, 

 the embryo of Gordius being armed with oval spines, thus 



Fig. 119. Gordius aquaticus. A, cgc: ; B, egg undergoing segmentation of the 

 yolk ; C, embryo (gastrula) with the primitive stomach, an infold of the outer ger- 

 minal layer of cells (ectoderm) ; D. embryo farther advanced ; E, larva, with the 

 three circles of spines retracted within the oesophagus; F, the same stage greatly 

 enlarged to show the internal organs ; c, middle circle of spines, the head being 

 retracted; m, muscular layei (?) ; t, beak or proboscis; i, intestine ; z. z, embryonal 

 cells ; /, excretory tube leading from </, the secretory glands ; on, oesophagus ; ?;, rec- 

 tum ; 11, anus. G, the second larva, encysted m a fish (after Villot). H, Gordius 

 varius, end of body of male, much enlarged. 1, Gordius aquaticus, end of body 

 of male, much enlarged. K, (iordins aquaticus, natural size. (LJ, I, K, drawn from 

 nature by J. S. Kiugsley.) 



reminding us in this respect of Echinorhyncli-i, but the em- 

 bryos, larva? and adult have a well-developed alimentary 

 canal. 



