THE INTEGUMENT AND THE EXOSKELETON 121 



laries, thus allowing them to expand and retain the blood at 

 the surface where the excess of heat can be constantly thrown 

 off. Thus repeated observations have been made in Samoa* 

 when whites and natives have been together and doing the 

 same work, that the skin of the latter would be dry and glow- 

 ing as in a fever, while that of the former was cold and damp. 

 Under these circumstances the Samoans would be constantly 

 giving off heat while the whites were compelled to retain theirs. 

 In the presentation of the above facts in connection with 

 one another, the conclusion seems almost unavoidable that the 

 various conditions are directly due to the solar action upon 

 each individual, and to the propagation of the conditions thus 

 acquired until the physiological advantages become inborn in 

 the race. Although this may seem at first the simpler expla- 

 nation, there are numerous biological facts associated with 

 heredity that seem to render impossible so direct a transmis- 

 sion of somatic peculiarities, and point to a more indirect 

 method of attaining the same end through individual variation 

 and the selection for survival in each generation of those in 

 which the desired peculiarity is the most marked. This ex- 

 planation, however, is in many points as unsatisfactory as the 

 other when applied to this case, since we know that the strug- 

 gle for existence in man has never been severe enough to 

 compel the extinction of individuals differing from others by 

 a shade of color; neither is sexual selection operative here, 

 since among a primitive people all who are not physically unfit 

 become the propagators of the race. The matter must be left 

 at present as one in which the facts are evident but the explana- 

 tion of them obscure; the problem is to be solved sometime, 

 and when solved will offer an explanation of the relation of 

 structure to environment everywhere. 



* According to Dr. A. Kramer. Die Samoa Inseln, Stuttgart, 1903. 



