General Morpliology 7 



be found developing together in a single diverticulum (see Crabb, 1927, 

 p. 75). It is thought by most malacologists that the spermatozoa ripen 

 first, descend during copulation, and are stored in the spermatheca of the 

 female system until the ova ripen and descend through the oviduct, and 

 that fertilization occurs when the ova and sperm meet in the lower part of 

 the uterus or vagina, just before the depositing of the egg capsule. Some 

 cytologists declare that fertilization occurs in the ovotestis diverticulum 

 and that the fertilized egg descends and is deposited without the necessity 

 for copulation. See Clapp 1927 for a discussion of this subject. Typical 

 eupyrene spermatozoa and nucleated o^'lm^: of Gyraulus circumstriatus 

 (TryonI are shown on plate 52, figs. 14-16. 



The Penial Complex, The male organ, which I have called the penial 

 complex, contains a number of features which are of great value in sys- 

 tematic diagnosis. The whole organ is divisible into two parts, a lower 

 swollen or bulbous portion called the preputium (PR) and an upper portion 

 called the vergic sac (VS). The latter contains the penis proper or verge 

 (V), which may be short and fat (plate 1, fig. 5, Planorbis planorbis) or 

 very long and narrow (plate 10, fig. 6, Drepanotrema hoffmani). All 

 grades of length and diameter between these extremes are to be found in 

 the different genera. 



The verge may be modified at its extremity by the presence of a dagger- 

 like object called a stylet (plate 16, fig. 6, ST, Gyraulus deflectus obliquus; 

 plate 14, fig. 1 and fig. 6 Gyraulus albus) . In these examples the outlet 

 canal for the passage of the spermatozoa is at the side. In other genera 

 there may be a fleshy papilla or appendage at the end of the verge (PA) 

 with the outlet of the canal in the middle at the base of the papilla (plate 

 2, figs. 5, 6, Segmcntina nitida) . In still other genera the termination of the 

 verge is simply rounded with the canal outlet in the center (plate 38, fig. 15, 

 Moietus cooperi calioglyptus) . Other slight modifications are found in 

 some genera. 



Between the vergic sac and the preputium there is an organ which I 

 have called the diaphragm (D). This is a muscular ring which separates 

 the two parts of the penial complex. This may be a simple ring with a 

 central perforation (plate 39, fig. 7, Menetus cooperi) or it may be a 

 dependent papilla (plate 23, fig. 6, Helisoma anceps; plate 24, fig. 10, 

 Helisoma trivolvis; plate 16, fig. 5, Gyraulus deflectus obliquus). The 

 preputium always has several vertical ridges on the inside called pilasters 

 (PL) which may serve to guide the verge or the penial gland during 

 protrusion. 



In 1926 (Trans. Wis. Acad., V. 22, pp. 200, 201) the writer called atten- 

 tion to a peculiar gland found in the preputium of the genus Helisoma. 

 Subsequent study has shown that this organ is found in several other 

 groups or genera of American, Euroi)ean, and Asiatic jilanorbids. This 

 gland is of variable shape, iiyriform, rounded, or elongated (plate 23, fig. 

 2, Helisoma anceps; plate 24, figs. 8 and 14, Helisoma trivolvis). In sec- 

 tion it is seen to be cup-shaped, to be lined on the sides with folds and to 

 have many small folds in the bottom of the cup. The gland is attached to 

 the inner wall of the preputium either midway between the male opening 

 and the muscular ring (diaphragm), or somewhat nearer this ring in some 

 species. 



