MODIFICATION OF THE GERM-CELLS IN MAMMALS 215 



which produced only fifty-eight offspring. Whether or not every 

 mating gave offspring is not definitely stated, but if so the aver- 

 age-size litter was unusually small, being only 1,81. This would 

 indicate either a stock of very low productivity or a high pro- 

 portion of absorbed embryos and partial abortions, as a final 

 result of which the litters would be small. In the foregoing 

 tables where the numbers of matings and young are very much 

 greater, not one group shows so small an average litter. From 

 the thirty-four matings of lead-poisoned males with normal 

 females, sixty-five offspring resulted, an average litter of 1.91, 

 and from twenty-seven matings of normal males with lead 

 females forty-seven young were born, an average litter of only 

 1.74. 



The fact that among the few individual litters recorded there 

 were three cases of litters of four, and five cases of litters of three, 

 makes it seem as though there may have been a high proportion 

 of mating failures, giving rise to the small average litters ob- 

 tained when the total number of young is divided by the total 

 number of matings. The distribution and cause of these mat- 

 ing failures, as is pointed out in the text above, may be of con- 

 siderable importance. 



Weller has analyzed his results in some detail. He takes into 

 account the influence of litter size on the birth weight and gives 

 several individual mating records which illustrate the effects of 

 a treated sire on the birth weight of the young from a normal dam. 



Weller has also taken into account the relationship between 

 lead dosage and birth w^eight of the offspring without finding 

 very consistent correlations. The relationship between germ 

 dosage and the condition of the offspring in our records may be 

 calculated for every individual born in the alcohol experiments, 

 3'et the result is uninstructive so far as at present studied. 

 There are a great number of confusing factors involved in this 

 seemingl}^ simple proposition. 



Weller' s final conclusions from the study of lead poisoning 

 closely accord with our previous statements regarding the influ- 

 ence of alcohol on the same animals. He finds that chronic lead 

 poisoning in guinea-pigs produces a definite blastophthoric effect. 



