EVIDENCE OF GERM CELL SELECTION 407 



the treated birds were all white and consequently, since they 

 were derived from the cross made in experiment 1, heterozy- 

 gous for color. These individuals should have developed two 

 kinds of germ cell with reference to their color-producing 

 potentialities, thus affording material for selection. Tables 3 

 and 4 show the results obtained. They do not reveal any ob- 

 vious effect of the alcohol unless it be in experiment 3, where 

 the percentage in A is considerably above what one would 

 expect. 3-C also shows a high percentage, and when it is 

 recalled that C followed immediately upon A, the probability 

 that the high percentage in both cases is due to a common 

 cause rather than to chance is somewhat increased. 



Except in 4-A, where the total number of individuals in- 

 volved is only 28, the percentage of white chicks does not fall 

 below 50 in any of the six separate experiments, the average 

 being over 53 per cent. This is rather close to expectation, 

 but the constant upward tendency of the white is at least no- 

 ticeable and suggests a possible inherent superiority of the white 

 producing germ cells. 



No very certain conclusion seems warranted in regard to 

 the effect of alcohol treatment upon the transmission of color 

 but in the experiment in which the treatment of the male was 

 most severe there is some indication that the germ cells bear- 

 ing determiners for the dominant character functioned more 

 commonly. 



In reviewing the four experiments, no. 3 will be seen to have 

 yielded the most striking results throughout. In this experi- 

 ment, not only did the three characters, brachydactyly, Poly- 

 dactyly, and color, show indications of the action of alcohol 

 vapor upon the germ cells, but the fertility of the eggs was also 

 markedly affected (table 2). This latter point is of interest 

 in connection with Pearl's results. One of the most constant 

 features reported in his paper is a regular elevation of the per- 

 centage of infertile eggs in his various alcohol series. When 

 the present work was begun similar results were expected, but 

 as will be seen by reference to table 2, they were realized only 

 in experiment 3. 



