38 



Dr. S. M. Copeman and Mr F. G. Parsons. [Dec. 1, 



supposition is strengthened by our experience that, in small litters, the 

 young are individually of greater size than we have found to be the 

 case in larger families. The difference between the percentages of 

 the large and small litters is not great enough to enable any general 

 conclusion to be drawn from it, but, so far as it goes, it suggests that 

 ample nourishment is more likely to result in an excess of male rather 

 than of female offspring. 



The next point to be discussed is whether the age of either parent 

 affects the proportion of sexes in the young. As an aid to the deter- 

 mination of this question the records of all the does of two months or 

 under at the time of conception, may be compared with those of all the 

 does of 6 months or over. 



We have records of 21 litters produced by does up to 2 months of 

 age. These give a total of 108 young, of which 55 (51 per cent.) are 

 males, and 53 (49 per cent.) females. With does over 6 months old we 

 have also records of 21 litters, with a total of 134 young; of these 74 

 (55 per cent.) are males and 60 (45 per cent.) females. These figures 

 show that there is an increase in the proportion of males to females in 

 the progeny of those does over 6 months of age. It will now be worth 

 while noticing that the does at intermediate ages, that is, from 2 J — 5 J 

 months (inclusive),' produced 27 litters, giving a total of 173 young, of 

 which 85 (49 per cent.) were males, and 88 (51 per cent.) females. 



Tabulated, we arrive at the following results : — 



This suggests that, in does over 6 months old, the proportion of 

 males to females increases, but we are unable to deduce anything from 

 this knowledge at present, for the reason that we do not know the 

 duration of the breeding period of a doe, nor at what stage the young 

 are likely to receive the greatest amount of nourishment. Moreover, 

 the difference in the proportion of the sexes among the young is not 

 a very great one, and, doubtless, there are many other influences at 

 work, the effect of which it is difficult to eliminate. One of these 

 is the tendency, of which proof has been adduced, that certain bucks 

 produce a preponderance of male or female offspring, but this 

 tendency, to a certain extent, has been neutralised by the fact that 

 our statistics have been drawn from the pairing of ten bucks with 

 twenty-eight does. It is unfortunate that the buck of which we 

 possess most records should have been paired so extensively with does 

 under 6 months of age, as had he been put with an equal number of 

 old and young does, it would have been interesting to have determined 



Does up to and including 2 months 

 „ between 2 J and 5 J months.... 

 „ of 6 months and over 



51 49 

 49 51 



55 45 



