266 



OLIGOCH AETA 



seurinalis; in Hemitubifex the penis is chitinous, and there is a vesicula serninalis. 

 The characters of these two genera, and of the three species of llyodrilus described 

 by EISEN, will be best shown in a table which follows : 



ILYODRILUS (STOLC). 



Nephridia with 'brown gland.' 

 Spermiducal glands, like that of 



Lumbriculidae. 

 Penial setae. 

 Spermatheca globular and sessile. 



ILYODRILUS (EISEN). 



Nephridia without that gland. 

 Spermiducal glands, as in Tubifex. 



No penial setae. 

 Spermatheca with duct. 



There may be other points of difference ; but in any case it seems to me that the 

 first two are amply sufficient to distinguish the European llyodrilus from its supposed 

 American congeners. 



Ilyodrilus coccineus, VEJDOVSKY. 



Tubifex coccineus, VEJDOVSKY, SB. Bohm. Ges. 1875, p. 193. 

 T. rivulorum (in part.), MACINTOSH, Trans. Eoy. Soc. Ed. 1870, p. 253. 

 T. rivulorum var. coccineus, VEJDOVSKY, Syst. u. Morph., p. 46. 

 llyodrilus coccineus, VEJDOVSKY, ibid. p. 150, footnote. 



Definition. Brain with a median process in front, and with two processes in the middle 

 line behind at origin of visceral ne.rves. Spermatliecae globular ami sessile ; genital setae 

 sometimes without notch. Hab. Europe. 

 The synonymy of this species is a little confused. There seems to be no doubt 



