1863. | Proceedings of the Asiatie Society. 69 
to the meeting that the theory of specific centres, or in other words, the 
restriction of species as a rule to definite areas was the only assumption 
made by Messrs. Blanford in their paper, and so far from being dis- 
proved by Mr. Theobald it had been actually strengthened by his 
division of India into provinces, each of which had its peculiar Mollusca, 
That species were thus restricted as a rule was admitted by naturalists, 
almost without exception, and it was on this ground that the Messrs, 
Blanford had sought to explain the observed exception in the case of 
the hill faunas of Southern India. Carriage of Mollusca on floating 
wood was admitted to be exceptional and rare, but cases of the kind 
had been observed and experiments made which proved its possibility. 
It is true that no migratory instinct is known in snails, but, given 
increase of numbers and power of locomotion, and an extension of 
species over an increased area would necessarily follow until re- 
strained by adverse conditions. As to the ethnic centres of the 
human race, it was observed that because, as argued, the sub-divisions 
of a species had sprung from definite centres, there was no reason to 
infer that the progenitors of these sub-divisions had not likewise 
sprung from a common centre. ‘The sporadic origin of species is not 
held by any eminent naturalists of the present day, and Mr. Theo- 
bald had advanced no instance in its favour. Mr. Blanford further 
denied that there was any evidence of the limitation of variability in 
species, and pointing out that Mr. Theobald had advanced no argu- 
ments in support of his own view, gave instances to prove, that 
variation is known to such an extent that the variety is no longer 
eapable of interbreeding with the parent stock : moreover, that many 
of our domestic varieties of animals and plants have become so much 
altered that the parent stock is either unknown or can only be indi- 
cated with doubt. 
Mr. Blanford concurred generally with Mr. Theobald’s division of 
India into sub-provinces, but would make some alterations therein. 
The President proposed that the thanks of the meeting should be 
given to Mr. Theobald for his interesting paper, which would appear 
in the Journal in the usual course. The Society were especially 
indebted to the gentlemen of the Geological Survey of India, who, 
in the course of their travels and researches over the length and 
breadth ofthis country found so many opportunities of sending papers 
to the Society. 
