EVIDENCE OF GERM CELL SELECTION 411 
not be inconsistent with the conclusions of this paper if it should 
turn out that within certain limits heterozygous individuals 
may produce functional germ cells of reciprocal classes in dif- 
ferent proportions, the average ratio for all individuals being 
in most cases about 50 : 50, but in brachydactyly, for example, 
39 : 61. Such a tendency, unless very marked, would be masked 
in ordinary breeding experiments since individual departures 
would be attributed to chance and lost in the totals. The 
data in the present paper happen to be so arranged that there 
are eight opportunities to note the correlation between per- 
centages produced by the same male parents in two differ- 
ent tests, and in all of these cases the correlation is positive. 
This is a matter that seems to be worth investigating and 
these data suggest a favorable method for attacking the prob- 
lem. To test the question properly, many matings between 
pairs or small groups of animals of proper gametic constitution 
should be made, and the data from these matings broken up 
into blocks that could be compared with each other and with 
similar blocks from other matings. 
SUMMARY AND CONCLUSIONS 
These experiments were planned to test the possibility of selec- 
tion between the different classes of germ cells produced by a 
heterozygous parent. For a selective agent alcohol vapor, which, 
inhaled through the lungs, is believed to pass directly into the 
circulation and thence to the fluids surrounding the germinal 
tissues, was administered to fowls of the desired genetic con- 
stitution. As an index of any selection that might occur, the 
relative proportion of certain traits, brachydactyly, polydactyly, 
and white color, appearing in the offspring produced during 
periods of treatment was compared with the proportion of 
those traits produced during control periods. The results 
indicate that with at least some traits selection is possible and 
and that it is more rigorous the more severe the treatment. 
Since, under certain conditions, here artificially produced, it 
appears that germ cells with different genetic potentialities 
