138 HEREDITY AND SELECTION IN SOCIOLOGY 



of which were nourished abundantly, while others were more 

 or less starved, have amply demonstrated this fact. In the 

 second place, we have to inquire how far modifications effected 

 by outside influences are capable of being transmitted by heredity. 

 If such modifications are non-transmissible, the influence of the 

 modifying conditions can only make itself felt as long as these 

 conditions actually prevail. Each newly bom individual is 

 affected in an identical manner ; but if these modifications are 

 not transmitted, they cannot become a permanent characteristic 

 of the species, although, owing to their uniformity, they may 

 present such an appearance as long as they last. 



The question of the transmission of modifications acquired 

 under the influence of environmental conditions has been 

 sometimes raised in order to try to justify the LamarcMan 

 theory of the transmission of acquired somatic characters. In 

 reahty, as we shall see, the question can be reduced to two aspects, 

 neither of which affords any justification of the LamarcMan 

 hypothesis. Either modifications acquired under the influence 

 of environmental conditions are hereditary — and in this case 

 there is nothing in the least surprising about the fact, for it is 

 extremely likely that the reproductive cells will be affected by 

 profound changes in the temperature or in the nutrition ; or else 

 such modifications are not hereditary — and this is certainly 

 true in a large number of cases. 



The last case may be illustrated by the galls which are 

 developed on plants. The gall is wholly useless to the plant, 

 and therefore there can be no question of adaptation, of any 

 receptivity on the plant's part to the insect which produces the 

 gall. The latter is developed solely by the direct action of the 

 larva, which exerts a stimulus on the surrounding cells of the 

 plant strong enough to affect considerable modifications. What 

 the precise nature of this stimulus is we are not able to state 

 with certainty ; it is, however, very probable that the move- 

 ments and salivary secretions of the larva effect certain changes 



