^g8 J. PERCY MOORE. [Vol. X. 



Of described species two belong to Bdellodrilus, viz. : B. illu- 

 minatus, and B. philadelphicus = Astacobdella philadelphica 

 Leidy (Pro. A. N. S. Phila., 1851, p. 209). Briefly these are 

 distinguished as follows: B. illuminatus — Head narrower than 

 the tapering anterior body segments. Dorsal jaw a compressed 

 dentigerous ridge, passing between the large paired teeth of 

 the lower jaw. There are nine pairs of conspicuous lateral 

 glands in the nine anterior body somites. Spermatheca 

 slender, and bifid dorsally. Penis freely eversible. B. phila- 

 delphicus — Head much broader than the anterior body seg- 

 ments. Both jaws triangular, the dorsal provided with a single 

 apical tooth, the ventral with a pair of smaller ones. No 

 lateral glands. Spermatheca broad, thin-walled, and sub-cylin- 

 drical. Penis proper not eversible, but carried to the exterior 

 by the eversible bursa, into which its projecting end is re- 

 ceived. A conspicuous prostate, in addition to a large glan- 

 dular sperm-sac. 



In the matter of technical manipulation Bdellodrilus illumi- 

 natus offers somewhat greater difficulties than other Discodri- 

 lidae. These arise chiefly from the presence of the relatively 

 enormous lateral mucous glands, which envelop the resting 

 body in a mass of glairy secretion, interfering with the ready 

 penetration of fixing fluids. The best preparations for anatom- 

 ical study were obtained by suddenly pouring over active 

 individuals hot corrosive sublimate solutions, especially that 

 recommended by Lang for fixing planarians. The latter 

 caused instant death and complete extension. Flemming's 

 chromo-aceto-osmic acid mixture gives the usual excellent 

 results as regards fidelity of fixation of histological structures, 

 and is particularly useful in the study of spermatogenesis, for 

 which the Discodrilidae are favorable subjects (see Voigt). 

 For the special study of the chlorogogue cells osmic acid is 

 useful. Perenyi's fluid, Merkel's fluid, potassium bichromate, 

 chromic acid, and picro-sulphuric acid did not give useful 

 results with this species, though not objectionable with B. 

 philadelphicus and other species. Narcotization with chloro- 

 form was successful; while alcohol was worthless for this pur- 

 pose. As to stains, either Delafield's or Kleinenberg's 



