i860.] LYELL'S CRITICISMS. 1 29 



fore has probably been long introduced, and they now speak 

 of Cretacean fossils there. But the first necessary step has 

 to be shown, namely, of a bat taking to feed on the ground, 

 or anyhow, and anywhere, except in the air. I am bound 

 to confess I do know one single such fact, viz. of an Indian 

 species killing frogs. Observe, that in my wretched Polar 

 Bear case, I do show the first step by which conversion into 

 a whale " would be easy," " would offer no difficulty " ! ! So 

 with seals, I know of no fact showing any the least incipient 

 variation of seals feeding on the shore. Moreover, seals wan- 

 der much ; I searched in vain, and could not find one case 

 of any species of seal confined to any islands. And hence 

 wanderers would be apt to cross with individuals undergoing 

 any change on an island, as in the case of land birds of Ma- 

 deira and Bermuda. The same remark applies even to bats, 

 as they frequently come to Bermuda from the mainland, 

 though about 600 miles distant. With respect to the Ambly- 

 rhynchus of the Galapagos, one may infer as probable, from 

 marine habits being so rare with Saurians, and from the ter- 

 restrial species being confined to a few central islets, that its 

 progenitor first arrived at the Galapagos ; from what country 

 it is impossible to say, as its affinity I believe is not very 

 clear to any known species. The offspring of the terrestrial 

 species was probably rendered marine. Now in this case I 

 do not pretend I can show variation in habits ; but we have 

 in the terrestrial species a vegetable feeder (in itself a rather 

 unusual circumstance), largely on lichens, and it would not 

 be a great change for its offspring to feed first on littoral 

 algae and then on submarine algae. I have said what I can 

 in defence, but yours is a good line of attack. We should, 

 however, always remember that no change will ever be 

 effected till a variation in the habits or structure or of both 

 chance to occur in the right direction, so as to give the organ- 

 ism in question an advantage over other already established 

 occupants of land or water, and this may be in any particu- 

 lar case indefinitely long. I am very glad you will read my 

 dogs MS., for it will be important to me to see what you think 



