139] LIFE HISTORY OF GORDIUS AND PARAGORDIUS—MA Y 19 



regarded as openings in the homogeneous cuticula. Furthermore, since 

 the dark collar is almost universally present in Gordiacea of this group, it 

 is probable that i^ was not actually lacking in the specimen of Du jar din; 

 and the fact that he overlooked this leads also to the possibility that he 

 overlooked a crescent that may have been present. The latter assumption 

 is moreover justified because there is at present no form known with a cuti- 

 cula that is devoid of true areoles and in which the male possesses no 

 crescent. Indeed Camerano makes the combination of presence of crescent 

 and absence of areoles a generic character. The use of the name Gordius 

 aquaticus by Villot seems justified in the light of these considerations. 

 But his description probably includes a group of closely related species 

 which some future investigator in Europe may be able to separate. 



Since there are several characters ascribed by various authors to the 

 European species that are not present in Gordius robustus the two species 

 can not be combined. Among the characters not present in Gordius robustus 

 are pseudoareolae, pores in the cuticula, a dorsoventral furrow at the pos- 

 terior end of the female, and groups of cells extending from the hypoderm 

 into the cuticula as described by Camerano (1888) and Rauther (1905). 

 The larva, also, of the European form appears to have a shorter body than 

 that of the American species. 



It is difficult to see why Montgomery assigned the American species 

 to Gordius villoti, since he himself states that Leidy's descriptions are 

 sufficient to establish the identity of the species and he had Leidy's material 

 at hand for additional information if necessary; furthermore, he certainly 

 was aware of the fact that Leidy's first description was given in 1851 and 

 his second description in 1879, while that of Rosa did not appear until 1882. 



HABITS OF ADULTS 



Gordius robustus emerges from its host during September and October 

 and possibly the latter part of August. Specimens may then be found 

 swimming freely in the streams or stranded at the water's edge. It is at 

 this time that they are most easily obtained in general collections. But 

 the period of migration does not last very long as the specimens soon be- 

 come entangled in the grass and debris along the edge of the water. 



During November and December I have still succeeded in finding 

 specimens in the grass just below the level of the water in small brooks. 

 Even at this time they tend to accumulate at or just below rapids. During 

 January and February I have made no collections, but the latter part of 

 March, when the ice has gone, specimens are again found in the grass. At 

 that time I have usually found them deeper down, entangled in the roots 

 of the grass even several inches in the ground. 



During April and early May there seems to be another migration on 

 the part of some of the worms, but I have never found them free in the 

 water. Since worms in captivity will usually remain quiet during the day 



