1 62 Heredity and Eugenics 



The effect upon 276' was an immediate production of the maxim mil 

 melanic condition, which was retained throughout the four generations 

 of experimentation, and lost only when 276^ was returned to control. 



In Experiment 27 there was no artificial selection, all imagines being 

 allowed freedom to mate and breed as in nature; hence the only 

 selective influences present were those exercised in the mating of the 

 beetles and by the conditions of the experiment, which eliminated a 

 small percentage. 



From the data of this experunent the following conclusions are 

 derived: 



1. A deviation in an environmental complex at once causes the 

 polygon of somatic variation and the modal class to shift as far from 

 the normal as it can go imder the given condition, and keeps them there 

 imtil there is a return to the normal environmental complex, when the 

 somatic variations also at once return to their normal state. 



2. The color variations employed in experiment, which are purely 

 somatic, are the direct result of a response to changed environmental 

 conditions, in terms of increased or decreased activity in pigmentation. 

 They may change as rapidly, as frequently, and in as many directions 

 as the conditions producing them change, and they have no influence 

 whatsoever upon the coloration of succeeding generations. 



This experiment, one of the earliest in my series, illus- 

 trates fairly well the results obtained in several others 

 carried out with the same end in view. In all, the result 

 has been a uniform one, and entirely against the idea of 

 transmission of somatic modifications. I have had many 

 instances when I thought at first that a somatic transmission 

 had taken place, but in all, further analysis and repetition 

 clearly showed some defect in experimentation; and in no 

 case have I been able to duplicate one of these occurrences, 

 much less obtain experimental proof of somatic transmission 

 in a repetition of the experiment. 



It is unfortunate that so many of the published experi- 

 mental investigations of this subject are open to diverse 



