40 



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



1. That the number of males born is slightly larger than that of 

 females. 



2. That certain males beget a markedly large proportion of male, 

 and others of female offspring. 



3. That there is some evidence that this tendency is hereditary. 



4. That certain does tend to bear an excess of either male or female 

 •offspring, but the evidence of this is not so conclusive as in the case 

 of the male. 



5. That mice bear inbreeding between a male and his offspring for 

 five generations without loss of fertility or apparent bodily degenera- 

 tion — this inbreeding in our one series of experiments being attended 

 with a large excess of female offspring. 



6. That the average number of young in a litter, judged from 

 seventy-three litters, is 6 '7. 



7. That in large litters more of the young are likely to be eaten by 

 the mother than in small ones. 



8. That in large litters the proportion of females is greater than in 

 small ones. 



9. That more males are produced by does over 6 months than is the 

 case with does under that age. 



10. That the temperature and time of year at which impregnation 

 occurs seem to exert little or no influence on the proportion of male 

 and female offspring. 



Of course the larger the number of experiments the greater will be 

 the likelihood of obtaining reliable statistics, so that it will be interest- 

 ing to determine whether another year's breeding confirms or 

 neutralises the results now recorded, but we think it desirable to 

 publish our observations at this stage, for two reasons, firstly, to invite 

 criticism on our methods and suggestions for future work, and, 

 secondly, to indicate to other breeders clues which would appear worth 

 while following up. 



It should, perhaps, be mentioned that, in each instance, careful record 

 has been kept of the colour of the individual mice mated together, and 

 also of that of their progeny. These results we have handed over to 

 Mr. Bateson, by whom they have been utilised in connection with 

 his investigation of Mendel's theory of inheritance of parental 

 characteristics.* 



* ' Zool. Soc. Proc.,' 1903, vol. 2, p. 83. 



