SPECIAL ANATOMY. 229 



oriians, tlie dart sac and multifid vesicles, are so com- 

 mon in European species, they are very rare in American 

 species. In not one of the latter does the flagellate form 

 of penis exist. A rudiment, or simplest condition of the 

 multifid vesicles, only exists in four species ; S. inter- 

 texta and H. gularis, in which there is a single pair of 

 folhcles, and H. ligera and H. siqjj^ressa, in which there 

 is but one short follicle. The dart sac exists certainly 

 in only the four latter species, probably in II. berland- 

 eriana, and doubtfully in H. concava. 



BuLiMUS. In B. fasciatus the penis is long, cylindri- 

 cal, and strongly muscular. The vas deferens joins it 

 near the summit ; and the retractor muscle, which is 

 very long, is inserted into the latter. The oviduct is 

 long, and its central part presents the peculiarity of be- 

 ing colored brown. The genital bladder is ovate, situated 

 near the ovary, and its duct is narrow, and as long as 

 the oviduct. The vagina is broad and muscular. At 

 the base of the penis, there opens a short, cylindrical 

 duct, derived from a single, multiBd vesicle, which pre- 

 sents six or seven rounded or ovate divisions. There is 

 no dart sac. 



In B. dealbatus the penis is very long ; its upper por- 

 tion is narrow and very tortuous, and flagellate in appear- 

 ance ; although the true flagellum, or the free portion of 

 the summit of the penis beyond the insertion of the re- 

 tractor muscle, is very short. The lower third of the 

 penis is dilated, and presents an annular constriction ; 



