222 HUGH WATSON. 



its occurrence in Philadelphia, Cape Town, and Auckland is due 

 to the agency of man. Testacella maugei occurs not only 

 in the south-west of England, but also in Portugal, Madeira, 

 and the Canaries ; and it seems to me that it might easily 

 have been transported to South Africa from any of these 

 localities, amongst the roots of plants. For the species of 

 Testacella are especially common in the rich soil of gardens 

 where worms are abundant; and it is known that under 

 adverse conditions a specimen can surround itself with a sort 

 of cocoon of hardened slime which protects it from drought, 

 and may remain dormant in this state for several weeks. 



It will be seen from PI. XXIV, fig. 159, that in some of the 

 South African specimens the posterior end of the penis is 

 curved round in a peculiar manner, and the retractor muscle 

 is attached to the vas deferens, a short distance in front of it.^ 

 Possibly this unusual arrangement may have been partly 

 caused by the way in which the animal contracted when it 

 was killed, for it only occurred in some shrivelled specimens, 

 which, in other respects, seemed to be identical with the 

 rest. 



Figs. 157 and 158 represent two of the shells labelled 

 "T, aurigaster" in the MacAndrew collection at Cam- 

 bridge. The first shows the usual shape of the shell in 

 T. maugei, while the second may be assigned to the variety 

 aperta Taylor,^ a form which was originally described from 

 the Azores. 



THE AFFINITIES OF APERA AND TESTACELLA. 



The Evolution of Carnivorous Characters. 



Both Apera and Testacella undoubtedly belong to the 

 group of the Stylommatophora comprising the carnivorous 



' The junction of the retractor muscle with the vas deferens is also 

 shown in Webb's figure of the genital organs of T. maugei (' Journ. 

 of Malac.; 1897, vol. vi, pi. vi, fig. 3). 



■^ ' Monog. L. and F.-W. MoUusca Brit. Isles,' 1902. vol. ii, p. 24, pi. i, 

 fitr. 15. 



