156 THE THEORY OF MUTATION 



to the influence of the environment upon the larval 

 stages of the beetle are not inherited ; but if the female 

 is subjected to abnormal conditions for a few days at 

 the time when the eggs are maturing, the eggs and 

 larvae being afterwards allowed to develop in the 

 normal environment, a greatly increased number of 

 mutations is obtained, the majority of which are the 

 same as those found much more rarely in Nature. 



MacDougal, too, has met with some success in the 

 attempt to produce mutations artificially in plants. 

 In one or two cases, after injecting weak solutions of 

 different chemical substances into the young ovaries 

 of Raimannia and (Enothera, seedlings were obtained 

 which differed from anything previously seen. Up to 

 the present time these successes seem to be too few in 

 number to allow of any definite conclusions being based 

 upon them. 



Blaringhem has also recently published observations 

 which seem to show that in the maize-plant injuries to 

 the parent occurring previously to the differentiation 

 of the germ cells may lead to permanent modifications 

 in the offspring. In neither of these three sets of 

 experiments did the modification produced in the off- 

 spring shpw any trace of an adaptive relation to the 

 exciting cause which operated upon the parent. 



So much may be stated in order to indicate the 

 direction in which research is proceeding. In the 

 course of another decade we may hope perhaps to 

 find out something more about the natural and artificial 

 production of mutations. 





