4 yo THE POPULAR SCIENCE MONTHLY. 



tion preceding that of Weismann ? and why he presents these 

 difficulties to me more especially, deliberately ignoring my own 

 hypothesis of physiological nnits ? It can not be that he is igno- 

 rant of this hypothesis, since the work in which it is variously 

 set forth (Principles of Biology, §§ 66-97) is one with which he 

 is well acquainted: witness his Scientific Evidences of Organic 

 Evolution ; and he has had recent reminders of it in Weismann's 

 Germ-plasm, where it is repeatedly referred to. Why, then, does 

 he assume that I abandon my own hypothesis and adopt that of 

 Darwin, thereby entangling myself in difficulties which my own 

 hypothesis avoids ? If, as I have argued, the germ-plasm con- 

 sists of substantially similar units (having only those minute 

 differences expressive of individual and ancestral differences of 

 structure), none of the complicated requirements which Dr. 

 Romanes emphasizes exist, and the alleged inconceivability dis- 

 appears. 



Here I must end : not intending to say more, unless for some 

 very urgent reason, and leaving others to carry on the discussion. 

 I have, indeed, been led to suspend for a short time my proper 

 work only by consciousness of the transcendent importance of the 

 question at issue. As I have before contended, a right answer to 

 the question whether acquired characters are or are not inherited, 

 underlies right beliefs not only in Biology and Psychology, but 

 also in Education, Ethics, and Politics. — Contemporary Review. 



THE COLOR CHANGES OF FROGS. 



By Pkof. CLAKENCE M. WEED. 



ONE who, with observant eye, leisurely paddles among the 

 water lilies of an inland lake must often notice how closely 

 the colors of the various frogs resting upon or among the lily 

 pads resemble their environment. In the open sunshine, where 

 light green is the prevailing tint, the colors of the frogs closely 

 approximate it, but in the dark and shady recesses of the forest- 

 bordered banks the batrachians are dull, deep brown, with darker 

 spots scattered over their bodies. These are the effects as seen 

 from above. If one were to dive beneath the water and look up- 

 ward, he would see in either case only the whitish undersides of 

 their bodies and legs — if, indeed, these were visible against the 

 general lightness of the upper world. 



It is evident that this resemblance to environment might re- 

 sult in either of two ways: first, the light-colored frogs might 

 seek the light surroundings and the dark ones the dark surround- 

 ings; or, second, the frogs, provided they had the power, might 



