1907] Beebe: Geographic Variation in Birds. 1 



ation of some factor of the environment acting as a stimulus to 

 produce a modification of coloration. 



7 — The variations produced by somatic stimuli are never 

 inherited, no matter how long the stimuli be applied. They are 

 therefore of no importance in evolution. They are of importance, 

 however, in a consideration of the phenomena of place and geo- 

 graphical variation. 



8 — Species of high variability in nature are also highly 

 variable in experiment, and conversely, those which are con- 

 stant in nature are the same in experiment; hence the observed 

 variability of a species is a good index of the presence or ab- 

 sence of somatic plasticity but is not necessarily an indication 

 of its ability to produce germinal variations and become a factor 

 in evolution. 



"Permanent, heritable color modifications of Leptinotarsa 

 have been found in nature, and are indistinguishable from so- 

 matic variations excepting in their capacity for being trans- 

 mitted to subsequent generations. They, however, have no rela- 

 tion to the variations experimentally induced herein described." 



Writing of the mutation theory in animal evolution. Prof. 

 Davenport mentions black plumage and color of iris among other 

 "discontinuous characteristics," and goes on to say, "One who 

 sees the striking failure of these characteristics and many others 

 to be modified in any important way will feel convinced that 

 they are not capable of forming intergrades, and hence could not 

 have arisen gradually." 



I have quoted from these various authorities in full to show 

 what diverse views on the subject are at present rife among 

 biologists, and how little we actually know not only of the direct 

 action of the various climatic factors of the environment, such 

 as temperature, humidity and light, upon terrestrial vertebrates, 

 but of the relative importance of these factors both in the onto- 

 genetic and phylogenetic history of the various organisms. The 

 most important phase of the subject and the one about which, 

 if possible, we know least, is the difference of inception and as- 

 similation of the various externally exerted stimuli, bringing 

 about non-inheritable somatic variations on the one hand, and 

 on the other, the heritable variations of the germ plasm; both, 

 in many cases, superficially so similar, and yet in their cumula- 

 tive influence so radically unlike in relative importance. 



Concerning the radical effects of a new environment acting 

 within historical times, Darwin relates of the Porto Santo rab- 

 bits, that in less than 440 years they had "decreased nearly three 

 inches in length and almost half in weight of body," besides 



