44 ILLINOIS BIOLOGICAL MONOGRAPHS [164 



OBSERVATIONS ON PARAGORDIUS VARIUS 



On account of the excellent description of the adult organization of this 

 species by Montgomery in 1903 and on account of the general similarity in 

 the development of this species and the one just described, the following 

 description will be made as brief as possible. 



DETERMINATION OF THE SPECIES 



Nothing needs to be added to the descriptions of this species given by 

 Montgomery (1898, 1903) except that here also, as in Gordius robustus, 

 there are present two longitudinal, darker bands; a broader dorsal and a 

 narrower ventral band. They are even more distinct than in the previous 

 species. 



HABITS or THE ADULTS 



This species prefers quiet water to rapids and more frequently inhabits 

 lakes than streams. It is not very abundant in the waters about Urbana, 

 but is the common species reported from the Great Lakes region. Nothing 

 has been observed in regard to the winter habitat. The earliest specimens 

 were taken near Urbana the latter part of May, 1914. At Douglas Lake 

 large numbers were emerging from their hosts the latter part of June, 1915. 

 While at Urbana both males and females were found in the grass at the 

 water's edge, only males were found in similar positions at Douglas Lake. 

 Females that had emerged during the night could still be found swimming 

 near the shore, but during the entire summer of 1915 only a few females 

 were found that had wound themselves around grass and had laid eggs. 



Females that have just emerged, while swimming near the shore, soon 

 encounter males and copulation takes place. The deposition of eggs begins 

 the following day. On June 27, 1915, an adult female was removed from 

 a host. It was kept alone in an aquarium until the 29th, when it was placed 

 with a male in a large vial and mating was observed. The next morning 

 it was found to have laid a string of eggs. Another female removed from 

 the host on June 30 and mated on the same day laid eggs July 1. Other 

 similar cases were observed. 



Mating was observed in several cases. The process is in every respect 

 similar to that described for Gordius robustus. The male more actively 

 responds to the stimulus from the female and the discharge of sperm is al- 

 most instantaneous. There is again no choice of direction and discharges 

 of sperm may in some cases take place at other parts of the body of the 

 female than the posterior end. There is no interlocking of the lobes at the 

 posterior ends of the two specimens, and after copulation the spermatozoa 



