1921.] N. Annandai.E & R. B. S. Sewell : Vivipara. 231 



border is connected with the loop of the intestine by an interven- 

 ing fold of thin membrane. Of the four surfaces of the kidne>', the 

 upper lies just under the skin against the shell. The apex of the 

 kidney lies to the front, and the left surface forms the- upper part 

 of the tight-hand wall of the mantle cavity and is in close relation- 

 ship with the terminal portion of the branchial fold. The base of 

 the kidney, which is triangular in shape with the apex of the 

 triangle directed ventrally, faces backwards towards the upper 

 part of the visceral hump and forms part of the anterior bound- 

 ary wall of the pericardial chamber. The right surface of the 

 kidney is in relationship v\ith the upper part of the ureter, which 

 separates it from the testis in the male or the uterus and shell- 

 gland in the female. A thin fold of membrane passes outwards 

 and backwards from the right-hand border of the base of the 

 kidney to the testis in the male and the shell-gland in the female 

 and forms the upper boundary limit of the ureter. 



Tiie kidney is provided with two orifices that open respec- 

 tively into the ureter and the pericardium. Both these apertures 

 are situated close together near the right posterior border. The 

 reno-pericardial opening is situated on the posterior or pericardial 

 surface of the kidney near the supero-external angle : it is oval 

 in shape and has thin walls. The external or ureteral orifice is 

 situated on the external surface, close to the reno-pericardial 

 aperture, but separated from it by the conjoined pericardium and 

 wall of the ureter. It possesses thick protuberant lips, which 

 are covered with ciliated, columnar epithelium and are often 

 marked by a ring of black or brown pigment. The ureter is a 

 thin-walled tube having in cross section a triangular lumen. Its 

 right wall is bounded by the testis in the male or the uterus 

 and part of the albumen- and shell-glands in the female : the left 

 wall is thin and separates it from the branchial chamber, while its 

 upper or superficial wall is formed partly by the rectum and 

 perirectal blood sinus and a thin-walled portion in contact with the 

 superficial skin. The orifice of the ureter lies, as we have already 

 seen, near the right-hand margin of the niantle edge, in the angle 

 between the rectum and the vagina in the female, or in the 

 corresponding position to the left and above and behind the anus 

 in the male. 



The Genital System. 



Vivipara hengalensis like all members of the genus is dioe- 

 cious, or in other words the two sexes are separate. We have 

 already seen that sexual differences are apparent in the structure 

 of the right tentacle, which in the male is thickened and recurved 

 and acts as a penis or intromittent organ. This change does not 

 seem to have proceeded quite as far in Vivipara hengalensis as in 

 the European species Vivipara vivipara, for in the former the 

 modified tentacle is sickle-shaped, whereas in the latter it is 

 figured as being completely contracted up into a rounded projec- 

 tion {vide Fischer, 1887, fig. 501, p. 733), which may actually be 



