146 



THE AMEBIC AN NATURALIST 



[Vol. L 



in the different-size litters. Almost 86 per cent, of the 

 individuals born one in a litter lived, and about 87 per 

 cent., 40 out of 46, of those born two in a litter lived. 

 When there were three in a litter, however, only 61 per 

 cent, lived and of those born four in a litter, it happened 

 that only one third of them survived, though there were 

 only a few in all. Of the total number of young from 

 normal non-related parents 74.44 per cent, lived. Judg- 

 ing from these statistics litters of one or two young are 

 the most vigorous and individuals born in litters of three 

 or four are not so likely to be strong and long-lived. 



The next space below gives the mortality records, 

 which, of course, is merely another way of bringing out 

 the above statements. The space following contains the 

 number of deformed animals, but from the normal mat- 

 ings not one such individual has been produced. The 

 last space gives the number of small-size or dwarf speci- 

 mens also, none of which occur among these litters from 

 normal non-related parents. 



The second vertical column contains a similar analysis 

 of the influence of the size of the litter on the mortality 

 and condition of the young born from non-related alco- 

 holic parentage. This not only includes the offspring 

 from directly treated animals, but also other matings of 

 non-relatives belonging to the alcoholic lines. Here 

 again the majority of all the young, 53.36 per cent., are 

 born in litters of two. Litters containing three are next 

 in frequency, followed by litters of only a single individ- 

 ual. Of the total number of offspring produced by al- 

 coholic parents 21.69 per cent, occurred in litters of three, 

 and only about 4 per cent, of the offspring were members 

 of litters of four individuals. The average number of 

 young in the litters from these animals is 1.79, somewhat 

 smaller than from normal matings. 



The space below shows that in all only 46.13 per cent, 

 of these young survived, whereas more than half as many 

 more, or 74.44 per cent., from normal parentage lived 

 over three months. The most vigorous animals are those 



