132 PROCEEDINGS OP THE MALACOLOGICAL SOCIETY. 



open, the whorls being in contact about half a turn from the apex. 

 The shell sometimes lay along the axis of the body of the crawling 

 snail, but it was generally held obliquely to the right, the direction 

 of the snail's head being indicated by the arrows in B and C. 



During life it was ascertained that the rectum opened on the 

 left side of the head. Luckily the body was obtained in good con- 

 dition, and dissection showed that the genital orifices were also 

 transposed to the left side. Anatomically, therefore, the specimen 

 is sinistral. As might be expected, its organs showed no gross 

 abnormalities, though I could not be sure of the asymmetry of the 

 pallial ganglia on the visceral loop, due to the osphradium, which is 

 generally plain enough,^ the right or left being the larger in dextral 

 or sinistral individuals respectively. The radula was normal. The 

 genitalia were well developed, but in serial sections I could find no 

 eggs or spermatozoa, the hermaphrodite gland being represented by 

 a mass of loose connective tissue. This may have been the result 

 of senility, but the presence of fairly normal lower genitalia is 

 apparently compatible with the absence of sexual cells, as was found 

 in the og form of Cochlicopa lubrica, described by Bowell.^ From an 

 early age it could be seen that the apical 2 or 3 millimetres of shell 

 was empty of viscera, which suggests that the gonads failed to 

 develop. The apical viscera were small and looked wasted as they 

 do in elderly pereger ; histologically, the liver and intestine were in 

 good order. The snail probably died of old age. It was just about 

 12 months old, and my experience as far as it goes of similar 

 pereger in captivity is that they generally die between 10 and 

 18 months, which corresponds to what one deduces from observations 

 in the field. 



P. Pelseneer ^ has seen shells without any spiral twist in Paludina 

 vivipara, Littorina rudis, Furjmra lapillus, Limncea stagnalis, PJiysa 

 ancilla, and Pk.fontinalis, but only in embryos, and he says (p. 401) 

 that such forms are not viable. Unfortunately I do not know what 

 the condition of the embryos was in the present case. Among 4,782 

 cousins which hatched and were examined, I found only two more 

 abnormal shells, one scalariform and one which started in a normal 

 sinistral spiral and then began to expand on the flat ; both died 

 young. Of the three dextral brothers two have survived, and in 

 them the rectum opens on the right ; similarly, the survivors of the 

 twenty-eight sinistrals defaecate on the left. They are, therefore, 

 presumably complete dextrals and sinistrals, and afford no evidence 

 that this flat shell is objective evidence of hyperstrophy.* 



^ See fig. 423 in Taylor's Monograph, vol. i, 1897, p. 214, for L. pereger, or 

 fig. 102 in A. H. Cooke's " MoUusca ", Cambridge Natural History, 1895, p. 204, 

 for L. stagnalis. 



^ These Proceedings, vol. xii, 1917, p. 313. 



' Les variations et leur hiriditA chez les mollusques, 1920, p. 354, and especially 

 fig. 234, p. 342. 



* J. W. Taylor, Monograph, vol. i, 1895, p. 110. 



