General Morphology 5 



near the male openinti; wlicre it is concealed in the muscular tissue of the 

 neck of the animal and appears again near the female opening (plate 24, 

 fig. 15 1. In some species the vas deferens is enlarged as it enters the vergic 

 sac, the enlargement being similar to the epipliallus of the land snails 

 (plate 39, fig. 7, Mcnetus). 



In one group of species (the Helisomatinae) there is usually a duct 

 (pcnial gland duct, plate 24, fig. 11, DC) which normally lies coiled at a 

 point between the vergic sac and the preputium (plate 27, fig. 9, DCO). 

 This may be very long, as in HelUoma trivolvu (i:)late 24, fig. 11) or short, 

 as in Hclisoma anceps (plate 23, fig. 3, DC). In another subfamily (Planor- 

 binae) there is no ])enial gland duct except in two or three genera. 



There are one or two retractor muscles of the penial complex (plate 24, 

 fig. 11, RM; plate 39, fig. 9, RM; plate 34, fig. 2) and a number of muscles 

 believed to be supporting muscles to retain the penial complex in position. 

 The retractor muscles enter the columellar muscle but the supporting 

 muscles are attached to the muscular wall of the forepart of the body. 

 The supporting muscles may in a measure perform the office of additional 

 retractor muscles in some genera, especially in helping to retract the pre- 

 l)utium after eversion. There do not appear to be any protractor muscles; 

 the penial complex becomes turgid by blood pressure. 



The penial complex assumes many shapes in the genera belonging to 

 the subfamily Helisomatinae. The preputium may be pushed upward and 

 the vergic sac may occupy a position on the side of the prei)utium as in 

 Helisoma campamdatum (plate 27, figs. 5-8). 



The vas deferens is continued near the female complex and borders 

 the uterus and oviduct where it is a small tube (plate 24, fig. 15, Helisoma 

 trivolvis). Just above the spermatheca the prostate appears. This organ 

 varies greatly in the different genera. In Helisoma (plate 24, fig. 15, PRS) 

 it is somewhat elongated and fan-shaped and the compound diverticula 

 empty directly into the sperm duct along a very small portion of that 

 tube. A cross section of the prostate in Helisoma trivolvis illustrates this 

 condition (plate 24, fig. 13; see also plate 27, figs. 4 and 12, cross sections 

 of Hclisoma ca)npamdatum) . The section is seen to be distinctly fan- 

 shaped. In some other genera the prostate duct is separated from the sperm 

 duct and vas deferens and the prostate is greatly lengthened. The prostate 

 is composed of many or few diverticula arranged in a single series, each 

 diverticulum being attached to and emptying into the separate prostate 

 duct, which in turn empties into the vas deferens below the prostate 

 (plate 14, figs. 7, 9; plate 1, figs. 1, 7). 



Bevond the prostate the vas deferens is continued as a somewhat larger 

 tube, the sperm duct (plate 27, fig. 14, SPD; plate 24, fig. 15). At its distal 

 end the sperm duct unites with the oviduct to form the ovisperm duct or 

 hermaphrodite duct (plate 27, fig. 14; plate 34, fig. 6). 



About midway of the ovisperm duct is a glandular enlargement which 

 has been called the seminal vesicle (SV). Many students of both fresh- 

 water and land pulmonates simply call this region an enlargement of the 

 ovisperm duct, but it is distinctly glandular and different from the ovi- 

 sperm duct in structure. It also occupies the position above the prostate, 

 where it lies in other animals. It is recognized as the seminal vesicle by 

 Simroth (1912, p. 501) and by Larambergue (1939, p. 94). Taylor (1900, 

 p. 359) calls the small sac-like organ into which the duct of the albumen 



