112 DiplommatinaHuttoni mid ^nnesihicolor in the West Lidies. 



be very probably transported with living plants, or with roots 

 or seeds. Mr. Guppy doubts whether the animals would sur- 

 vive the voyage from the East to the West Indies. Of this 

 there can, I think, be no question. Mr. Benson, if I am not 

 mistaken, has had specimens of Dijylomviatina alive in Eng- 

 land ; and there are very few Indian shells which, when sesti- 

 vating, will not bear a journey of several months without in- 

 jury, provided damp or excessive cold be avoided. 



That the introduction of a single pair of shells is ample for 

 the diffusion of the species has been proved in Calcutta in the 

 case of Achatina fuUca. The facts are well known, but will 

 bear repeating. About twenty-five years ago, two specimens 

 were brought from Mauritius, and placed in a garden. Now 

 the species abounds almost everywhere throughout an area of 

 at least five miles in length. In many places several hundreds 

 might be collected. Ten years ago, to my own knowledge, 

 the shell was quite unknown in the Botanical Gardens on the 

 opposite bank of the Hoogly. The other day I saw it living 

 there in abundance. Of course, in a large city like Calcutta, 

 where plants are constantly transferred from one garden to 

 another at a distance, great facilities for dispersion exist ; but 

 the numbers, all unquestionably derived from a single pair in 

 the course of so short a time, are nevertheless astonishing. I 

 have very little doubt that one impregnated female would suffice 

 equally well to introduce a species. 



Another fact in favour of Diplomrtiatina Huttoni and Ennea 

 licolor having been introduced into the West Indies by man 

 is, that both are very small shells, precisely such as would 

 most easily escape notice and be transported with plants. No 

 shell is more likely than the Ennea to have been thus carried 

 into foreign countries. The case of the Dijjlonnnatina is cer- 

 tainly far more difficult, but still it appears to me to present 

 fewer difficulties than the theory of migration. Is there a 

 botanical garden in Trinidad ? 



If the Dij^hmmatina has not been transported artificially, I 

 should be almost inclined to suspect that the Trinidad species 

 is not really identical with that inhabiting the Western Hima- 

 layas, but that two forms, closely resembling each other, have 

 originated separately at the extreme limits of the area occupied 

 by the genus. 



With regard to the Ennea^ I have very little doubt of its 

 having been transported. Many of the cultivated plants of 

 the West Indies must have been introduced by the Spaniards 

 and Portuguese, some of them, in all probability, direct from 

 India ; and the date of the introduction may thus have been 

 sufficiently distant to allow of a considerable amount of disper- 

 sion amongst the various islands. 



