igoS. BowELL. — Limnoia prcBlcmiis, n.sp., &* Z. glabra. 47 



slight differences which distinguish it from Z. mvohita were 

 uniformly present. The fragility of the shell may well 

 account for its rarity and isolation ; indeed, it is evidently not 

 made to be a " wanderer." 



As in all the ovate Limnaeas which I have examined, the 

 bulk of the female part of the epididymis and the albumen 

 gland was relatively very great ; so much so as to suggest 

 that extreme development of these parts may be the pre- 

 disposing cause of the ovate condition of the shell. In one 

 i7ivohcta examined, the volume of these parts was three- 



FlG. I. 



Fig. 2. 



Fig. I, Genital Organs of LimncEa pratenuis. Fig. 2, oi L. glabra. 



Magnified 5 times. 



quarters of that of the whole animal. Concutrentlj', the size 

 of the digestive glands is reduced, and the upper whorls 

 are shared about equally between these and the ovotestis. 

 One would naturally expect an animal of such propagative 

 construction to be short-lived ; and accordingly we find that 

 when adult it has only four whorls. With respect to relative 

 size of parts, L. glabra presents a converse condition. The 

 large specimens often to be seen in collections testify to its 

 capacity for longevity. 



Of the accompanying figures, Nos. i and 2 represent the 

 genital organs of L. prcetemus and L. glabra respectivel3\ 



A 2 



