4 The Molluscan Family Planorbidae 



The genital outlets are on the left side of the neck, the male opening 

 just behind the left tentacle and the female opening a short distance behind 

 the male opening in the side of the neck. In many individuals the penial 

 complex has been observed protruding from the male opening (plate 29, 

 figs. 6, 7, 11, 12), the animal having been killed while in breeding con- 

 dition. That self-impregnation of the female system by sperm from the 

 extended penial complex is possible is easily believed when the closeness of 

 the two sex outlets is observed. 



The body above the foot may be flatly rounded or it may be rounded 

 above and flattened on both sides of the foot (plate 70, fig. 10). Good 

 figures of the animal of Tropicorbis are shown on plate 78. 



The color of the animal differs in the various genera. Mostly it is 

 bluish-slate or blackish, grayish, or brownish, the color being lighter on the 

 base of the foot and on the tentacles. In some species the color is yellow- 

 ish. There are often flecks or spots of white on the foot and tentacles. The 

 mantle, especially over the lung and kidney, is in many groups heavily 

 blotched with black or brown. 



The shell may be carried perpendicularly, as in Helisoma (plate 70, 

 fig. 7) , or it may lean to the left sicle, causing the shell to be pseuclodextral 

 or ultradextral, as in Gyraulus and JMenetus (plate 70, fig. 9). 



B. GENERAL INTERNAL ANATOMY 



The internal anatomy includes the following systems: Reproductive, Di- 

 gestive, Respiratory, Renal, Circulatory, INIuscular, and Nervous. The most 

 important internal structure for classification purposes is the reproductive 

 system and this will be first considered. 



[a] The Reproductive System 



Like other Basommatophora, the Planorbidae are hermaphroditic with the 

 organs of the two sexes mostly separated. The difi^erent organs may be 

 tabulated as follows: 



' vergic sac 

 verge 

 sperm canal 



Female organs <{ nidamental gland diaphragm or 



muscular ring 

 preputium 

 penial gland 

 penial gland duct 

 pilasters 

 ^ muscles 



f ovotestis 

 ] ovisperm duct or 

 ] hermaphrodite 

 1^ duct 



Male Organs. External form. In the natural position the penial complex 

 lies over the vagina and uterus (plate 39, fig. 3). When pulled away from 

 this position its form is seen to be more or less cylindrical and to consist 

 of a large bulbous lower portion, preputium (PR) and a smaller pyriform 

 portion, the vergic sac (VS, plate 24, fig. 11). A narrow tube, the vas 

 deferens (VD) is inserted at the summit of the vergic sac. This descends to 



Male organs. 



vagma 

 uterus 

 oviduct 



nidamental gland 

 spermatheca 

 spermathecal duct 

 , albumen gland 



' penial complex 



vas deferens 



prostate 



prostate duct 

 , seminal vesicle 



Penial complex. 



Common to both 

 male and female. 



