70 ILLINOIS BIOLOGICAL MONOGRAPHS [190 



RELATIONSHIPS 



The results obtained in the present investigations afford new evidence 

 both in regard to the interrelationships of the group and their relations 

 to other groups. 



From the descriptions given in this report it is evident that the two 

 species studied differ widely in regard to the form and structure of the 

 larva, the participation of the proboscis in later development, the arrange- 

 ment of the parenchyma in the female, and the development of the adult 

 cuticula. An examination of the literature shows that these differences are 

 not confined to the species studied, but appear in the same grouping in all 

 cases where sufl&cient information is at hand to permit comparison. I have 

 myself examined larvae and also sections of adults of Chordodes sp. and 

 find an essential agreement in structure with Paragordius varius. The 

 larva of Chordodes is even more abbreviated than that of Paragordius, the 

 cuticular structures and the mesenteries are more pronounced, and the 

 esophagus is present in the adult. 



In view of these differences I believe that there exist in the present 

 family of Gordiidae two well defined, natural groups, one of which is 

 represented by the genus Gordius and the other by the three genera Chor- 

 dodes, Paragordius and Parachordodes. For that reason I propose to 

 retain the family Gordiidae for the genus Gordius and to establish a new 

 family, Chordodidae, for the other three genera. 



Since the position of the present family of Nectonemidae is not definite- 

 ly established, and since from the descriptions given Nectonema resembles 

 the nematodes and especially the Mermithidae in the structure of the 

 muscle cells, the alimentary canal, the hypoderm with its longitudinal 

 thickenings and lack of cell boundaries, the structure of the cephalic 

 ganglion, and in the location of the nerve cords within the thickening of 

 the hypoderm, it is not possible to retain the Nectonemidae in the order 

 Gordiacea. The family may for the present be assigned to an independent 

 position in the vicinity of the Nematoda. 



The limits of the old family Gordiidae then become the limits of the 

 order Gordiacea. 



The description of the proposed family Gordiidae may be given as 

 follows: Gordiacea with a smooth cuticula, presenting no true areoles. 

 Bristles on the body arising from the fibrous cuticula. Mouth, when cavity 

 is present, not connected with the intestine. Ovaries not enclosed by 

 mesenchyme and consequently no double mesenteries in the female. 



