6 The MoUuscan Fcunily Planorhidae 



gland enters, the seminal vesicle, but as this organ is an adjunct of the 

 male system in all animals it could scarcely be located in an organ of the 

 female system. The swelling near the albumen gland is the carrefour. The 

 seminal vesicle is variable in form in the different species and genera and 

 provides another feature for classification purposes (see plate 35, fig. 5, 

 Carinifex jacksonensis; plate 1, fig. 1. Planorbis planorbis; plate 14, fig. 7, 

 Gyraulus albus). 



Female Organs. The vagina ( VG) , usually a thick walled, wide tube, 

 passes imperceptibly into the uterus (U) which is usually much enlarged. 

 A large sacculated body, the nidamental gland (NG, sometimes called 

 egg gland) follows the uterus and is usually placed over the uterus and the 

 oviduct. The oviduct (OD) lies back of the gland and is much narrowed 

 as it passes backward to join the ovisperm duct. The method of junc- 

 tion of the oviduct and sperm duct with the ovisperm duct varies in 

 different genera. 



The albumen gland (AL) is a large, more or less elongated organ, com- 

 posed of many small alveoli. In its natural position it lies over the stomach 

 and a loop of the intestine passes under it causing a channel to be formed 

 on the under side of the albumen gland (plate 38, fig. 9, Menetus opcrcu- 

 laris; plate 15, fig. 1, Gyraulus hirsutus) . The organic relations between 

 the albumen gland and the oviduct are somewhat complicated. A small 

 duct extends from the albumen gland and enters a large bulbous swelling 

 which is attached to the end of the oviduct before that organ combines 

 with the sperm duct to form the ovisperm duct. This gland or bulb is the 

 carrefour which receives the products of the albumen gland and from which 

 they enter the oviduct (see plate 34, fig. 6, Carinifex ponsonbyi; plate 35, 

 figs. 6, 7, Carinifex jacksoriensis) . Taylor (1900, p. 359) erroneously calls 

 the carrefour the seminal vesicle. 



The spermatheca or receptaculum seminis (S) is a bulbous or pear- 

 shaped organ with a narrow duct of variable length which enters the 

 vagina at its junction with the uterus. Its function is said to be that of 

 receiving the sperm (in the form of a spermatophore) during copulation 

 and to store it safely until the eggs descend from the ovotestis, at which 

 time they are fertilized by the stored sperm. The vagina is usually very 

 short but may be of considerable length in some species. 



Organs Common to Both Systems. The ovotestis (OT) is embedded 

 in the liver and fills about one whorl of the shell. It varies in form much 

 as does the prostate, the two organs being more or less synchronous in this 

 respect, a valuable feature in classification. In the Helisomatinae it is 

 many-lobed, the diverticula branching fan-wise from the ovisperm duct 

 (plate 27, fig. 4, Helisoma campanulatum ; plate 34, fig. 9, Carinifex pon- 

 sonbyi). In the Planorbinae and Scgmentininae the diverticula are in pairs; 

 the two diverticula are attached directly to the ovisi)erm duct (plate 

 16, fig. 9, Gyraulus deflectus obliquus) . During the breeding season the 

 diverticula may be filled with both ova and sperm, the ova either ripe 

 for expulsion or developing (plate 10, fig. 2, OT, Drepanotrema hofjmani). 

 The ovisperm duct is a small tube of variable length, enlarged near the 

 middle to form the seminal vesicle. 



Both ova and sperm are produced in the same diverticulum. They are 

 said to arise simultaneously from indifferent epithelial substance and may 



