366 PROCEEDINGS OF THE AMERICAN ACADEMY. 



In his Chapter XIII. of "The Germ Plasm," Weismann gives an in- 

 teresting example of the inheritance of climatic variation in butterflies. 

 After an account of his recent experiments on Polyommatus Phlceas, he 

 states: " Both experiments, however, prove the correctness of the old 

 assumption of lepidopterists that the action of heat on a single gen- 

 eration is capable of giving the German form of a blackish tint; and 

 since, moreover, it is clear that the development of a single generation 

 at a lower temperature can render the color of the Neapolitan butter- 

 fly less black, it appears that the two varieties may have originated 

 owing to a gradual cumulative influence of the climate, the slight 

 effects of one summer or winter having been transmitted and added 

 to from generation to generation. This would then seem to be an 

 instance of the transmission of acquired characters." He then adds, 

 that he does not believe that this is the correct interpretation of the 

 facts; on the contrary he insists: "The theory of determinants will 

 I believe supply a very simple explanation of this apparently compli- 

 cated case, which I consider of great value, because it confirms this 

 theory. Instead of supporting the doctrine of the transmission of 

 somatogenic characters, this example shows how such a process may 

 apparently be brought about, and on what it depends. A somatogenic 

 character is not in this case inherited, but the modifying influence — 

 the temperature — "ffects the primary constituents of the wings in 

 each individual, — i. e. a part of the soma — as well as the germ 

 plasm contained in the germ cells of the animal. It modifies the same 

 determinants in the rudiments of the wings of the young chrysalis as 

 in the germ cells, namely, those of the wing scales," etc. 



We certainly prefer the more simple explanation first given, but 

 only to be rejected, by Weismann, since it appears to be really based 

 on observed facts, and to be a natural and logical induction from such 

 facts, and is thus a more scientific explanation. The same process of 

 reasoning will apply to the inheritance of acquired characters in the 

 ontoo-eny of the Lepidoptera and that of other groups, such as we have 

 endeavored to set forth in this essay. 



It is, moreover, a simple and natural inference, such as in the case 

 of the butterflies experimented on by Weismann, and would be the 



New York Entomological Society, I. 22-28, 57-76; Proceedings Amer. Phil. 

 Soc. Philad., February, 1893, pp. 83-108, March, 1893, pp. 139-192; Proc. Amer. 

 Acad. Arts and Sciences, Boston, 1893, XXVIII. 55-92 ; Annals New York Acad. 

 Sei., May, 1893, VIII. 41-92. Also Monograph of the Bomhycine Moths of 

 North America, Part I., in course of publication in the Memoirs of the National 

 Academy of Sciences, Vol. VII. 



