176 PROCEEDINGS OF THE AMERICAN ACADEMY 



in NeiDaul, — any more than that patches of Alpine vegeta- 

 tion, wholly of Labradorian species, were separately created 

 on Mount Katahdin in Maine, the White Mountains of New 

 Hampshire, and a few summits of the Green Mountains and 

 Adirondacks. , 



As respects the vegetation of former epochs, so far was 

 Professor Gray from conceding " that the present distribution 

 [of plants] was linked with that of earlier periods in a man- 

 ner which excluded the assumption of extensive migrations, 

 or of a shifting of the flora from one area to another," that he 

 was, on the contrary, struck with the remarkable dissimilar- 

 ity between the early tertiary and the more ancient floras of 

 Europe and America and that now existing ; for example, the 

 miocene flora of the coast of Oregon being very like that 

 of Switzerland of the same period, and in both a tropical flora 

 of predominant Australasian types ; the eocene flora of at 

 least some parts of Europe being prominently Australian ; 

 the flora of Europe, even since the creation of some existing 

 species, possessing numerous North American types of which 

 there are now no representatives whatever on that conti- 

 nent, &c. 



In conclusion Professor Gray remarked, that, when we 

 speculate about the origin of species, we launch out beyond 

 the region of induction, and have only analogies or probabil- 

 ities to guide us, which we have to weigh one against another 

 as well as we can. And he deemed it very important to the 

 progress of science that different investigators should start 

 from independent and opposite preconceptions or lines of 

 thought. His preconception was that of the local origina- 

 tion of species ; not origination in single individuals or single 

 pairs, — which might or might not be the case in different 

 species. The improbability of single origin appeared to him 

 to be great in the lower grades of animals ; the probability of 

 it greater and greater as we rise in the scale of being. But 

 the local origination of each species appeared to him not 

 only the natural hypothesis to begin with, as he had before 



