THE ANATOMY OF BDELLODRILUS ILLUMI- 

 NATUS, AN AMERICAN DISCODRILID. 



J. PERCY MOORE. 



Introduction. — The present paper is devoted to a descrip- 

 tion of the general anatomy of Bdellodrilus illuminatus, with- 

 out much attention to histological detail, or any discussion of 

 the special evidence which this species affords, pro and con, on 

 the matter of current views regarding the zoological relation- 

 ship of the family. The latter is reserved for a future paper, 

 which awaits the completion of embryological studies now in 

 progress, as well as a more thorough knowledge on the part of 

 the writer, of the extensive literature of oligochaete and hiru- 

 dinian anatomy. 



Bdellodrilus illuminatus was originally described, under the 

 tentative name of Branchiobdella illuminata, in the Proceedings 

 of the Philadelphia Academy of Natural Sciences, 1893, p. 421 ; 

 since which time more thorough anatomical studies, and the 

 examination of additional native species of Discodrilidae, and 

 of the European Branchiobdella parasita (specimens of which 

 were kindly obtained for me by my brother, Mr. H. F. Moore, 

 from Dr. Anton Collin), have forced me to the opinion then en- 

 tertained, that this species should constitute the type of a dis- 

 tinct genus. 



This it is proposed to name Bdellodrilus, as being at once 

 suggestive of probable affinities with the Oligochaeta, and of 

 special structural modifications in the direction of the leeches. 



The genus is defined by the possession of the following 

 characters, all of which distinguish it from Branchiobdella. 

 There are two pairs of testes and two pairs of vasa deferentia 

 occupying the fifth and sixth post-cephalic somites. The 

 anterior pair of nephridia open to the exterior by a common pul- 

 satile vesicle. The dorsal and ventral jaws are quite dissimilar. 

 Branchiobdella possesses but one pair of testes and ducts, sepa- 

 rate nephridial pores, and similar dorsal and ventral jaws. 



