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THE AMERICAN NATURALIST [Vol. XLIII 



pigment-bearing scales, are fairly common. This condition 

 probably arises through an inhibiting action of the environment 

 upon the "scale mother cells." 



An interesting case of an environmental effect which is not 

 easily reversed is given by Marchal (3). Lecanium corni, a 

 scale insect, becomes L. robiniarum when reared upon Fobinia 

 pseudo-acacia instead of its normal food plants, but the reverse 

 experiment does not succeed. 



Salamanders are a close second to insects as favorite material 

 for the experimental study of the effects of the environment. 

 Powers has contributed a valuable paper (4) on the causes of 

 variation in Ambly stoma tigrinum and promises proof that cer- 

 tain of these are inherited or at least perpetuated by reason of 

 inheritance. Differences in the amount and character of the 

 food produce remarkable modifications in the structure of the 

 animal. If, as is hinted, variations in the appetite are inherited, 

 we should have an interesting case of indirect transmission of 

 characters. Among the conclusions the author says : 



" Specific characters, in species which vary as A. tigrinum varies, 

 are, after all, strongly determined by environing conditions. There is 

 nothing new in this. But the study of this species seems to me to lend 

 it new weight and confirmation. If the broad head and large teeth of 

 the cannibal are acquired characters — and they conform to the defini- 

 tion of such — what are the narrow head and smaller teeth of the cus- 

 tomary daphnid-feeder? Are these specific and congenital characters? 

 They are more frequent, more " typical " in the species, but I am forced 

 to conclude that they are so chiefly because daphnids are numerous and 

 constitute a convenient and stimulating food. And the same may be 

 said of nearly all specific characters; so readily are they modified by 

 a changed environment that we must conclude they are, in reality, 

 equally determined even by an unchanged environment. Congenital 

 tendencies in such species are not definitely specific, but only in- 

 definitely specific. In this species, indeed, they are not always even 

 definitely generic." 



Mr. Powers naturally points out that many of our catalogued 

 "species" are merely ontogenetic and believes that "the zoologist 

 must soon admit that the final test of many species must lie in 

 the rearing, and that, too, under controlled conditions." We 

 may, perhaps, go further and say that this is the test of all 

 species, but that it is not worth while to apply the test in all cases. 

 It is probably true that many of our so-called species are not 

 orthodox species but are the results of reversible physiological 



