262 * RAYMOND PEARL 



not be attributed to differential treatment after hatching. This 

 result furthermore can not reasonably be supposed to be due to 

 any superiority in innate constitutional vigor in the parent stock 

 used in the case of the alcoholics. Such a supposition is defi- 

 nitely negatived by the pedigree data presented in I, and also 

 by the method followed of using sisters as controls. 



It will be noted that the results in respect of postnatal mor- 

 tality are exactly in accord with those already noted for pre- 

 natal mortality (p. 261). The progeny of treated parents have 

 a lower rate of mortality than the progeny of untreated. The 

 most probable explanation of all these results appears to be the 

 one which has already been suggested in dealing with prenatal 

 mortality, namely that the alcohol (or ether) acts as a selective 

 agent upon the germ cells, preventing the formation of zygotes 

 by any except the strongest and most resistant gametes. 



VI. THE SEX RATIO IN THE Fi PROGENY 



It has been claimed at various times and by various persons 

 that the general metabolic condition of the parents at the time 

 of conception is a factor in sex determination, or at least has an 

 influence on the sex ratio. Particularly convincing evidence that 

 this is the case in various species of rotifers has been afforded by 

 the recent papers of Whitney (43). Russo's (33) attempt to 

 demonstrate that in mammals the nutritive condition of the 

 germ cells is a hmiting factor in sex determination was not so 

 successful, Basile (1) and Punnett (32) failing to confirm his 

 results. It is of importance in any experiment like the present, 

 whatever one's a priori opinions about the probable outcome, to 

 examine with some care the sex ratios obtained, in order to see 

 whether by any chance the parental treatment has influenced 

 them in any way. In particular does such an examination 

 appear desirable in view of the recent statement by Stockard 

 and Papanicolaou (38, p. 166), in discussing the different results 

 in the two sexes of the progeny of alcoholized guinea pigs. They 

 say: 



