286 RAYMOND PEARL 



ground of too low germ dosages as compared with mammalian 

 experiments until we have definite statistics regarding mam- 

 malian experiments which shall show for each individual sepa- 

 rate mating, in actual tabulated figures (a) the total germinal 

 dosage prior to conception, using the term 'germinal dosage' 

 in the sense defined in this paper, (b) the number and quality of 

 offspring. 



We may now return to the further consideration of the second 

 possibility mentioned above, namely that the apparent dis- 

 crepancy between the avian and mammaUan results is funda- 

 mentally due to a difference in degree of resistance of the germ 

 cells to alcohol. On this basis it is possible, I believe, to frame 

 an hypothesis which will bring together in a satisfactory manner 

 under one point of view the apparently discrepant results of 

 Stockard, Pearson and the writer. 



At the outstart let us remind ourselves of a point which one 

 is apt to overlook in considering results of this sort, namely 

 that the germ cells which produce the zygotes, which are the 

 progeny of our experiments, are only a very minute fraction of 

 all the germ cells which the parents form. Let X be the total 

 number of germ cells (ova or spermatozoa) which the individual 

 produces, and let a be the number which succeed in taking 

 part in the formation of zygotes, and let A be the number 

 which do not so succeed. Then, of course, A = X — a, or put 

 the other way about, 



X = A +a 



This is the fundamental gametic equation. Starting from 

 this point let us attempt to develop, very briefly, a general 

 theory of the action of deleterious agents upon germ cells, and 

 then compare our experimental results with such a general 

 theory. We know that A is enormously greater than a. There 

 is furthermore a great deal of evidence that a is not a random 

 sample of X, but on the contrary is a highly selected sample. 

 To Roux in his ^Kampf der Theile' is to be given the credit for 

 first pointing out what now seems axiomatic, that there is con- 

 stantly going on a struggle for survival among the cells of the 

 organism, the physiologically 'best' being the survivors. To the 



