AMERICAN ZOOLOGISTS AND EVOLUTION. 13 



Prof. A. E. Verrill, 1 on the supposed eastern migration of the cliff- 

 swallow, traces historically its first appearance in various places in the 

 East, and is inclined to the opinion that as the country became settled 

 by Europeans the birds left their native haunts for barns and houses, 

 and increased in number to a greater extent than before on account 

 of the protection invariably furnished by man. 



Rev. Samuel Lockwood 2 records a curious case of the Baltimore 

 oriole acquiring a taste for the honey-sacs of bees, tearing off the 

 heads of those insects, and, having secured the honey-sacs, rejecting 

 the rest of the body. 



Prof. Wyman 3 observes a curious case in Florida of a colt and a 

 number of pigs and cows thrusting their heads under water and feed- 

 ing on the river-grass, in some cases remaining with their heads im- 

 mersed for half a minute. 



Hon. A. II. Morgan 4 observes the widest difference in the habits 

 of the same species of beaver iu the Lake Superior region and in the 

 Missouri, constructing their dams and ways differently, and meeting 

 the varied conditions, not by a blind instinct, but by a definite intelli- 

 gence manifested for definite purposes. 



All of these facts, simple in themselves, yet together go to prove 

 that animals do vary in their habits, and with a persistent change in 

 habits arises the minute and almost insensible pressure to swerve and 

 modify the animal. 



So much does the influence of season, with its accompanying pe- 

 culiarities of food, temperature, humidity, and the like, affect certain 

 animals developing coincidently with its different phases, that it is 

 instructive to note that in certain species of insects two or three dif- 

 ferent forms occur. Thus Mr. Edwards 6 has in an elaborate way 

 worked up the history of a polymorphic butterfly [Ephiclides ajctx), 

 showing that there are three forms heretofore regarded as distinct 

 species, which are only varieties of one and the same species, but ap- 

 pearing at different times of the year, and consequently confronted 

 by different influences as to temperature, moisture, food, and the like. 

 These forms are known under the names of Walshii, Telemonides, 

 and JIarcellus, and both sexes are equally affected. The first form 

 mentioned represents the early spring type, Telemonides the late 

 spring type, and Marcellus the summer and autumn type {see also 

 Mr. Scudder's paper 6 ). If these influences affect species, we should 

 expect to see the greatest variety of forms in a country possessing 

 the widest diversity of conditions. 



Some suggestive paths of investigation have been pointed out by 



1 " Proceedings of the Boston Society of Natural History," vol. ix., p. 276. 

 a American Naturalist, vol. vi., p. 721. 3 Ibid., vol. viii., p. 237. 



4 " " The American Beaver and his Works." 

 6 " Butterflies of North America," part ix. 

 6 American Naturalist, vol. viii., p. 257. 



