296 RAYMOND PEARL 



14. There was no evidence that specific germinal changes have 

 been induced by the treatment, at least so far as concerns those 

 germ cells which produced zygotes. 



15. It is suggested that these results, as well as the results of 

 earlier workers, may be most satisfactorily accounted for on 

 the hypothesis that alcohol and similar substance act as selec- 

 tive agents upon the germ cells of treated animals. The essen- 

 tial points in such an hypothesis may be put in the following 

 way. 



a. Assume that the relative vigor, or resisting power of germ 

 cells varies or grades continuously from a low degree to a high 

 degree and fiu-ther assume that the absolute vigor of the whole 

 population of germ cells, measured by the mean let us say, is 

 different for different species. 



b. In the intensity of dosage employed in inhalation experi- 

 ments alcohol does not destroy or functionally inactivate all 

 germ cells. The proportionate number of the whole popula- 

 tion of germ cells which will be inactivated by such dosage may 

 fairly be supposed to depend upon the mean absolute vigor or 

 resisting power characteristic of the particular species or strain 

 used. In a species with germ cells of absolutely low mean 

 vigor proportionately more will be functionally inactivated than 

 in a species of high absolute mean vigor of germ cells. 



c. Besides the germ cells which are wholly inactivated by the 

 deleterious agent, and which we may designate as class (a), we 

 may fairly assume that there is a possibility of two other classes 

 existing, viz., (6) germ cells which, while not completely inacti- 

 vated, are so injured by the agent as to produce zygotes which 

 are measurably defective in some degree, and (c) germ cells 

 which are not measurably affected by the agent at all in the 

 dosage employed, and produce zygotes which are not discern- 

 ibly otherwise than perfectly normal. 



d. It appears entirely fair to assume that germ cells of the 

 (a) class are of relatively the lowest mean vigor or resisting 

 power, class (b) next, and class (c) the highest. The proportion- 

 ate number of the two sorts of zygotes corresponding to classes 

 (6) and (c) of germ cells which would be expected to appear in 



