MODIFICATION OF THE GERM-CELLS IN MAMMALS 175 



the evidence shown in table 2 this may readily explain the 

 apparent advantages. 



The last three columns show the results of the first two groups 

 combined and in addition contain a few records from mixed 

 cases that could not be properly included in any of the previous 

 classes; for example, animals with one parent of alcoholic ancestry 

 and the other parent directly treated, etc. 



Here again there is considerable contrast between the alcoholic- 

 father and the alcoholic-mother columns, these differences being 

 due to the influence on the totals of the Fi records from the 

 treated-father and treated-mother columns of the first group. 

 The productivity when only the father is alcoholic is low, the 

 litters being small and over 21 per cent of the matings result in 

 failure. It may be inferred that there was a rather high 'early 

 prenatal mortality.' The average litter weight, however, was 

 about as good as normal. The late prenatal and postnatal 

 mortality records are better than those from the alcoholic 

 mothers. 



The average-size litters from the alcoholic mothers was rather 

 large and the mating failures were much less frequent than from 

 the alcoholic fathers, indicating a lower probable 'early prenatal 

 mortality.' The average litter weight was lowxr than from alco- 

 holic fathers, taking into account the size of the litters in the 

 two classes. The total mortality from alcoholic mothers was 

 high and the proportion of late prenatal to postnatal was ex- 

 cessive. It is thus seen that a high prenatal mortality is fol- 

 lowed by a low, postnatal death rate, and this is in accord with 

 our assumption that a high 'early prenatal mortality' will be 

 followed by not only a low postnatal, but also a low late pre- 

 natal mortality. In other words, the more thorough the elimi- 

 nation of defective embryos and fetuses the greater the prob- 

 ability of survival for the selected few that remains to be born. 



The last column with both parents alcoholic has a mortality 

 record as good as the alcoholic-father column and better than 

 the alcoholic-mother, but this is only apparent and not real. 

 The column contains only one individual from directly treated 

 parents, and consequently the alcoholic treatment was applied 



