•93 



PROCEEDINGS OF THE ACADEMY OF 



[Feb., 



Fiii'.TI. — Male iudividual of D.conklini, 

 drawn from a living specimen. A, 

 dorsal surface ; B, lateral surface. 



confined in tlie egg capsule, together witli female eml^ryos, ])ut was 

 nevertheless fully formed and swimming about as freely as its limited 

 quarters would allow. In all essential characters it resembles the male 



of D. apatris Korsch. Its form 

 (text figs. II, A and B) is that of 

 a short cjdinder with rounded 

 ends, slightly constricted at its 

 middle. Al)out the anterior end 

 is a ring of cilia situated in a 

 groove. This ring is continuous 

 below with a strip of cilia clothing 

 the ventral surface. At its poste- 

 rior end was seen the outlines of 

 the conical penis, which is directed 

 downward and backward, as 

 Korschelt (1SS2, 1889) has figured 

 it. Of the interior of the body 

 little else could be discerned ex- 

 cept a number of refractive granules, which were prol^abh' sper- 

 matozoa. 



As will appear from a glance at the taljle of species given ])elow, D. 

 conklini stands very close to D. apatris Korsch. and D. gyrociliatus 0. 

 Sch. From D. apairis it differs in the proportions of head and trunk, 

 in the presence of dorsal gaps in the preoral ciliated bands, in having 

 but two large sense hairs instead of four, and in the presence of a cicum- 

 anal or terminal band. D. conklini moreover lacks a character which 

 seems to be distinctive of D. apatris, namel}', tliat of having the head 

 joined to the trunk b}" the intermediation of a short piece, which has the 

 appearance of a much shortened segment, without the ring of cilia. 

 The characters distinguishing D. gyrociliatus and D. conklini are much 

 slighter. Indeed the sole external difference distinguishing the two 

 species is the presence of the dorsal gaps in the two preoral bands of 

 cilia in D. conklini. This alone would seem far too slender a basis on 

 which to erect a new species, if it were not that it is accompanied by 

 considerable differences in the internal organs, the nephridia in par- 

 ticular. 



In the table below an attempt has been made to set forth in brief 

 form the distinguishing characters of the different species composing 

 the group, and the literature directly relating to each. That this table 

 is imperfect is certain, but this is due at least in part to the imper- 

 fectness of many of the descriptions, especially the earlier ones. Later 



