342 DARWINISM AND THE PROBLEMS OF LIFE 



transmitted to the offspring ? It is not necessary to 

 suppose this. We can just as well imagine that the 

 lower temperature affected the whole pupa, and even 

 penetrated to the germ-cells contained in it. As the 

 wings especially were affected by the cold, that may 

 have been the case with their determinants in the 

 germ-cells ; these being so profoundly influenced that 

 even after the cessation of the cold they brought about 

 modified wings. " Medium influences," such as climate, 

 for instance, can often not only modify an animal, but 

 also penetrate it and modify its determinants. 



Thus the experiment does not prove that the 

 modifications of an organ brought about by a 

 stimulus will on their side influence the corresponding 

 determinants in the germ ; the stimulus may reach 

 them directly. We do not know how far or how 

 often these medium influences on the germ may act, 

 and so we will not linger over this principle, once it 

 has helped us to take away an apparent support of 

 the Lamarckian theory. 



The explanations offered us by the hypothesis of 

 an orthogenetic action of constant stimuli are not 

 satisfactory. The Lamarckians say, for instance, that 

 certain mammals, such as whales and walruses, have 

 almost entirely lost their hairy coat owing to the 

 constant action of the water. In other animals the 

 water is said to have formed horny plates on the 

 mucous lining of the palate, as in the tortoises, the 

 duck-bills, and the whales. We may ask, then, why 

 the water has not reduced the fur of the otter, the 

 beaver, the seal, and the water-rat, and why we find 



