1 66 Ajiimal Life and Intelligence. 



colour of the surroundings; and that the larvae of the 

 emperor moth (Saturnia carinni) spin dark cocoons in dark 

 surroundings, but white ones in lighter surroundings. 

 These are but samples of the interesting results Mr. 

 Poulton has obtained. 



What shall we say of such cases ? Some of them seem 

 to indicate the very remarkable and interesting fact that 

 changes of salinity of the medium, or changes of food, or 

 the more general influence of a special climate, may modify 

 organisms in particular and little-related ways. The larvae- 

 of a Texan Saturnia fed on a new food-plant develop into 

 images so modified as to appear new species. Changes of 

 salinity of the water modify one species of Artemia into- 

 another. If these be adaptations, the nature of the 

 adaptation is not obvious. If the new character produced 

 in this way be of utilitarian value, where the utility comes 

 in is not clear. The facts need further confirmation and 

 extension, which may lead to very valuable results. Mr. 

 Poulton's observations, on the other hand, give us evidence 

 of direct adaptation to colour- surroundings. But the effects 

 are, in the main, restricted to the individual. What is 

 hereditary is the power to assume one of two or three 

 tints, that one being determined by the surrounding colour. 

 His experiments neither justify a denial nor involve an 

 assertion of the transmissibility of environmental in- 

 fluence. Secondly, some of the cases above cited seem to 

 show clearly that, under changed conditions of life, the 

 changes which have been wrought in one generation may 

 reappear in the next. But are they inherited? Is there 

 sufficient evidence to show conclusively that the body-cells 

 have been modified, and have handed on the modification 

 to the germ? Can we exclude the direct action of the 

 more or less saline water, or the products of the unwonted 

 food on the germinal cells ? Can we be sure that there is 

 really a summation of results — that each generation is not 

 affected de novo in a similar manner ? No one questions 

 that the individual is modifiable, and that such modifica- 

 tion is most readily effected in the early and plastic stages 



