AMERICAN ZOOLOGISTS AND EVOLUTION. n 



of the main field. This interpretation of arctic forms on high peaks, 

 though attended to by several American naturalists, is not new. Os- 

 wald Heer, in discussing the origin of certain animals and plants, 

 coincides with De Candolle that Alpine plants are relics, as it were, 

 of a glacial epoch. Prof. Gray ' had also independently arrived at 

 the same conclusions, based on a comparison of the plants of Eastern 

 North America and Japan. In the position he maintained regarding 

 the derivation of species from preexisting ones, he stood far in ad- 

 vance of his brother naturalists in this country, for this was before 

 Darwin's great work had appeared, and before Heer had developed 

 the host of fossil plants from the arctic zone. Mr. S. I. Smith, in 

 speaking of mountain faunae, points out the gradual encroachment of 

 glaciers, and the drawing down of northern forms ; and, as the gla- 

 ciers retreated, these forms were caught, "the mountain-summits 

 being left as aerial islands." Dr. Packard and Mr. Scudder have 

 severally called attention to the same thing. 



Prof. A. R. Grote has more fully dealt with the subject in a paper 

 read before this Association, and in a graphic way shows that the 

 "former existence of a long and widely-spread winter of years is 

 offered in evidence through the frail brown OEneis butterflies, that 

 live on the top of the mountains within the temperate zone." I have 

 been thus explicit, in order to contrast these more rational views with 

 those formerly entertained by eminent naturalists, whose minds were 

 imbued at the time with the idea of special creation. Mr. Samuel H. 

 Scudder 2 read before the Boston Society of Natural History an ac- 

 count of distinct zones of life on high mountains, as illustrated in the 

 insect-life of Mount Washing-ton. He called attention to certain insects 

 which he supposed peculiar to the summit, and not found farther 

 north, though showing a remarkable correspondence to certain arctic 

 forms. Prof. Wyman asked whether all the facts might not be ac- 

 counted for on the theory of migration northward after a glacial 

 epoch, and Prof. Rogers suggested that the facts might be accounted 

 for on the migratory theory if we added thereto the supposition of 

 subsequent variation induced by isolation. Yet these views were 

 persistently opposed by the other naturalists present. The mass of 

 evidence already contributed, as to the extraordinary variation in 

 color, markings, and size of species coinciding with their physical sur- 

 roundings, though perhaps trivial in itself, becomes important when 

 the proofs are grouped together, and all bear upon the theory of 

 derivation. So slight a thins; as change of food is found to influence 

 certain animals even to a degree usually regarded specific. The late 

 Dr. B. D. Walsh 3 discovered some very curious features among in- 



1 "Memoirs of the American Academy," vol. vi., pp. 37*7-458 (1859). 

 3 " Proceedings of the Boston Society of Natural History," vol. ix., p. 230. 

 3 " On Phytophagic Varieties and Phytophagic Species," " Proceedings of the Ento- 

 mological Society of Philadelphia," vol. iii., p. 403. 



