424 MY LIFE 



forms that must have intervened ; but I can conceive verte- 

 brata and mollusca so developed ab initio. If this is all 

 Lewes claims, Darwin will, I am sure, admit it. If he main- 

 tains a distinct origin for mammals, birds, and fishes, how 

 does he deal with the identical forms of the embryos up 

 to a certain stage, which is still that of a vertebrate 

 animal ? 



But he never tells us what he does believe in detail, and it 

 seems to me that his views are utterly groundless if he goes 

 beyond the four or five primitive forms, which is all that 

 Darwin claims as essential to his system. 



" His notion of the mammals of Australia having possibly 

 developed ab initio is too wild to be seriously refuted, and I 

 think he gives it up in his last part, which you have not sent 

 me. What of the fossil marsupials in Europe? The identity 

 of embryos? The identity of bone, tooth, hair, and nail 

 structure? The identical general arrangement of vertebrae, 

 limbs, muscles, cranium, brains, lungs, tongue, stomach, and 

 intestines — all to have been developed independently through, 

 or out of, forms as low as medusas and actinias by general 

 similarity of conditions! It is too absurd ! " 



The subject on which Sir Charles Lyell and myself had 

 the longest discussions was that of the effects of the glacial 

 period on the distribution of plants and animals, and on the 

 origin of lake basins. On the former question he was dis- 

 posed to accept my views in opposition to those of Darwin, 

 as shown by the following letter of February 2, 1869 : — 



" Dear Wallace, 



" The more I think over what you said yesterday 

 about the geographical distribution of tropical animals and 

 plants in the glacial period, the more I am convinced that 

 Darwin's difficulty may be removed by duly attending to the 

 effects of the absence of cold. The intensity of heat, whether 

 in the sea or in the air, is not so important, as you remarked, 

 as uniformity of temperature." 



He then goes on to give illustrations of this, and urges 

 that there are no recent deposits in or near the tropics con- 



