364 JOURNAL OF CONCHOLOGY. 



ON THE MORPHOLOGY OF THE GONADS IN 

 LIMN^A STAGNALIS (L.) AND L. PEREGRA (Miill.) 



By J. W. WILLIAMS, M.A., D.Sc. 



(Read before the Conchological Society, July 4th, 1888, and approved by the referees). 



The reproductive organs (gonads) of the Pulmonata resolve 

 themselves into three groups — a male group, a female group, 

 and a group common to both the male and female portions. 

 From this arrangement the genus Limnsea forms no exception. 

 In Z. stagnalis the male group consists of a penis sac, a vas 

 deferens, and a well-defined prostata; the female group is made 

 up of a vagina, oviduct, receptaculum seminis or spermatheca, 

 albuminiparous gland and two, rarely three, accessory albumini- 

 parous glands developed along the course of the oviduct ; the 

 common group contains the ovotestis (hermaphrodite gland) 

 and its duct (hermaphrodite duct). The male and female 

 portions open to the exterior at different points on the right 

 side of the prostoma ; the former just below and slightly to the 

 right of the tentacle (penial aperture), the latter some distance 

 posterior to this (ostium vaginae). Self-fecundation, reasoning 

 on anatomical considerations, is possible ; and, according to 

 Macalister, in L. auricularia (where the same condition of the 

 position of the genital apertures obtains) this has been actually 

 observed ; but it is a matter of very great doubt whether such 

 self-fecundated ova would be fertile. The pe7iis is a botuli- 

 form sac, circularly striated on its exterior, smooth on its interior, 

 bent upon itself at a right angle, and lying in the coelom of the 

 prostoma to the right of the buccal mass and the commencement 

 of the cesophagus. It is grooved on its upper surface for the 

 prostata, and the proximal end of the spermatheca, the former 

 being the more anterior of the two. The vas deferens proprium 

 commences in a well-defined depression on the anterior surface 



J.C., v., Oct., 188S. 



