246 EMBRYOLOGY 



whether the life even in a single host may not prepare the 

 Gorclius for further development (Villot, No. 17). 



In addition to fishes, the Gordius larvae may also get into 

 frogs, insects, spiders, and Crustacea, although, according 

 to Villot, fishes are their most common hosts. As is well 

 known, the Gordiidee are often found also in terrestrial in- 

 sects, for example beetles and grasshoppers ; but nothing is 

 accurately known concerning the conditions of infection in 

 these animals. In insects of prey it can be explained as the 

 result of swallowing infected insect larvae. The extraordi- 

 nary size and development of the Gordiidae in such terres- 

 trial animals is explicable by the fact that they so long 

 lacked the opportunity of reaching the water, the place of 

 their final development. 



General Considerations. 



The systematic position of Gordius must be briefly considered here. 

 Vejdovsky has recently reverted to the idea, prevalent in former times, 

 that the Gordiidae present much closer relationships to the Annelida than 

 to the Nematoda, and perhaps are even to be looked upon as degenerate 

 Annelids (Nos. 14 and 15). The segment-like arrangement of the ova- 

 ries, and more especially the structural conditions of the body cavity, give 

 rise to this conception. The latter is said, according to Vejdovsky, to be 

 bounded, on its somatic wall at least, by a well-marked epithelium, and 

 the intestine, as well as the genital organs, is said to be united to the 

 body-wall by means of mesenteries. Villot denies the existence of the 

 mesenteries, and refers the epithelium seen by Vejdovsky to a kind of 

 mesenchymatous tissue, which in young stages of development fills up a 

 large part of the space between the intestine and the body-wall. There- 

 fore the body cavity of the Gordiidae, like that of the Nematoda, is bounded 

 on one side by the musculature of the body-wall, which arises from 

 that [mesenchymatic] tissue, and on the other by the entodermal wall of 

 the intestine itself. On the latter Vejdovsky even could recognize no 

 lining epithelium, a condition which he explained, however, by the great 

 reduction of the intestine. However, v. Linstow has also denied recently 

 the presence of an epithelium lining the body-wall (No. 12), and Came- 

 RANo, in consequence of the early stages of development of the Gordiidce 

 observed by him, argues for their relationships to the Nemathelminthes 

 (No. 11). Nevertheless the Gordiidte are distinguished from the Nematoda 

 by the peculiar condition of their genital organs and their deviations from 

 them in other systems of organs, especially the nerve-ring, which is pro- 

 longed into the ventral cord, and they can be co-ordinated with them as 

 a separate division. What was said in considering the Nematoda must 



