1907] Beebe: Geographic Variation in Birds. 33 



acquired color characters? If subjected to an environment of ex- 

 treme dryness would Scardafella ridgwayi assume the plumage 

 of S. inca ? Would other melanizing factors than humidity, such 

 as hemp food, bring about similarly orthogenetic series of 

 changes?* Is Scardafella especially plastic in response to ex- 

 perimentation, or does this plasticity reflect very recent variation 

 in the feral state? What would be the effect of applying these 

 conditions before the adult plumage is acquired? 



Have we in these unexpectedly radical changes of plumage 

 under humidity any hint or clue to the annual changes of many 

 migratory birds, such as the male scarlet tanager, indigo bunting 

 and bobolink, which assume brighter colors after a winter in the 

 humid tropics ? If so, why are the females immune from such in- 

 fluence? Considering Prof. Whitman's law, under these conditions 

 of experimentation, can the direction of evolution ever be an- 

 ticipated? These and a hundred other important aspects of the 

 problem all await solution. 



In regard to the all -important question of the inheritance 

 of somatic changes produced by external factors, we have for 

 comparison the aflfirmative facts given by Fischer, who produced 

 moths of dark colors by exposure to a low temperature and re- 

 ports that the offspring of two of these moths were also dark; 

 and the negative results of Tower, who after experiment upon 

 ten lineal generations of Leptinotarsa declares that "it is clearly 

 demonstrated that the somatic variations in color are not in- 

 herited, but that they are fluctuating, transient, and due solely 

 to environmental stimuli which accelerate or retard color de- 

 velopment." Tower explains the aflflrmative result by the appar- 

 ently logical reasoning that during the period of experimentation 

 in the case of the lepidopterous insects, the germ cells were in 

 the more sensitive stages and hence were directly affected by 

 the stimulus of cold, this being not the case in his own experi- 

 ments. If this is true, we have yet to await the demonstration 

 of the inheritance of a true acquired character — a phenomenon 

 which will doubtless never be forthcoming. 



E — Correlation with Natural Selection. 



The question will at once be raised by some, that my ex- 

 periments, as far as they go, indicate that natural selection has 

 little or nothing to do with such phenomena as protective colora- 



* As far as my experience goes, a diet of hemp produces in Scardafella an irregular 

 blotchy melanism, very different from that induced by humidity, but this is based on only 

 one individual. 



