1863. | Notes on the Indian terrestrial Gasteropoda. 305 
hills isolated from one another by tracts, in which, from physical 
causes, shells are absent ; hence it is argued, that at the period these 
colonists attained their present quarters, very different physical 
features and conditions must have obtained over the intervening area, 
to what now exist. In support of this they appeal to the geological 
history of the Peninsula, on which point I in no wise differ from them, 
but it seems to me that no necessity exists for appealing to any such 
agency to explain the distribution above mentioned, and that more- 
over it is utterly and beyond expression inadequate to promote the 
results attributed to it. 
In a former paper I alluded to the existence of several distinct 
Indian Provinces of land mollusca, to which very few shells are com- 
mon, and it is not less suggestive than singular that among the few 
shells common to two or more Indian Provinces, some of them trespass 
far beyond the geographical limits of India, even as far as Africa, 
Mauritius, &e. Now it is sought to be argued, that because some 
few shells such as Helix Huttont, B., H. Similaris Fer., H. Castra B. 
Bulimus punctatus, Anton, and some others, have a very wide range, 
that they must have migrated, inch by inch, over all the intervening 
space, or must have availed themselves of such means of conveyance 
as a conveniently submerged country, or the reverse of such a condi- 
tion, as supposition demands, afforded. 
A geologist certainly is not easily staggered by any considerations 
involving a mere question of time, but I confess that to me, more 
than ordinary ditliculty seems to be involved in the supposition of 
the case of these living travellers, restlessly diffusing themselves as 
though urged on by the furies of Orestes, or propelled by the desire of 
possessing the fairer pastures of a far off land. The migratory instinct 
of birds certainly offers an instance of an irresistible and spontaneous 
impulse from within to seek other climes, but I am aware of no facts 
which would lead us to suppose that any similar instinct or stimu- 
lus is implanted in the invertebrate classes, which would ensure or 
conduce to their dispersion. In such cases too, as Mr. Darwin suggests, 
(Origin of Species, page 397,) the means of transport afforded by winds 
and waves, is quite independent of any voluntary effort on the part 
of the animal, who, for many a weary day or week, must have concen- 
trated its energies to retaining hold of its straw or stick. The possi- 
bility of a small Helix being carried uninjured round the globe, 
