MODIFICATION OF THE GERM-CELLS IN MAMMALS 181 



In table 4, male and female ancestors treated does not neces- 

 sarily indicate that all records, in the column were derived from 

 matings between two alcoholic parents, since both males and 

 females may have been treated among either the ancestors of 

 the mother or the father, but not necessarily both. For this 

 reason the sixth and ninth columns of table 3, in which both 

 parents were in all cases from, alcoholic ancestry, show more 

 decidedly that two alcoholic parents when mated together give 

 the very highest early prenatal mortality, but a low late pre- 

 natal and postnatal mortality. This last conclusion is extremely 

 interesting in connection with Pearl's results on fowls. 



Pearl found that when two alcoholic fowls were mated to- 

 gether, the percentage of infertile eggs was higher than from 

 any other combination, while the prenatal mortality, embryos 

 dying in shell, and the postnatal mortality- were the lowest. 

 This is exactly what the guinea-pig records show, provided 

 our 'early prenatal mortality' (indicated by the small litter 

 size, the frequent mating failures, and the observed mortality 

 occurring in utero during all later stages of development) can 

 be considered the same as many of Pearl's 'infertile eggs.' 

 Without intending any adverse criticism of the designation 

 'infertile,' we may again suggest the possibility that a certain 

 proportion of these eggs had really begun development, but had 

 died in the early cleavage or gastrular stages, and yet on ex- 

 amination, other than a minute microscopic study, they ap- 

 peared as infertile or unfertilized eggs. If this were true, they 

 could be classed in the early prenatal mortality records. Such 

 an adjustment would serve to harmonize the fowl and guinea- 

 pig records in another important respect. 



Pearl has attributed the good qualities of the offspring from 

 his alcoholic parents to a germinal selection which has tended to 

 cause all weak germ cells to be completely put out of commis- 

 sion by the alcohol treatment and only the very best have sur- 

 vived to produce embryos, and these therefore show a low per- 

 centage of deaths in shell and a low postnatal mortalit}^ A 

 selection is also playing its role in the case of the guinea-pigs, 

 but here it is -not acting alone on the germ cells, but more evi- 



