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 aquat.icm. A, egg ; B, egg undergoing segmentation of the 

 yolk ; C, embryo (gastrula) with the primitive stoQiacli. 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 tlie oesophagus : Y, the same stage greatly 

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

 retracted ; in, muscular layei f?) ; l, beak or proboscis ; i, intestine ; z, z, emhi7onai 

 cells ; /, excretoi-y tube leading from g, the .secretory glands ; ob, oesophagus ; v, rec- 

 tu II ; ?i, anus. (j. the second larva, "encysted in a fish— (after Villot). H, Goi'dius 

 vaHus, end of body of male, much tnlarged. 1, Gordius aquaticas, end of body 

 of male, much enlarged. K, Gordius aguaticus, natural size.— (H, I, K, drawn from 

 nature by J. S. Kingslcy.) 



reminding us in this respect of Echinorhynchi, but the em- 

 bryos, larvae and adult have a well-developed alimentary 

 canal. 



