68 CHARLES A. COBURN 



12. The number of wild and savage females in each hybrid 

 generation is always greater than the number of wild" and sav- 

 age males. 



13. In the experiments in selective breeding it was generally 

 to be noted that there was a tendency for the degree of wildness 

 or savageness possessed by the parents to be reproduced in the 

 offspring, that is, if both parents were wild, (the average of 

 their third, fourth and fifth tests for wildness being equal to or 

 exceeding 2.5 grade), in the majority of cases it would be found 

 that the number of wild offspring was greater than that of tame, 

 or if the parents were tame the greater number of offspring 

 would be tame. The occasional isolated case in which this 

 tendency did not maintain and where the results seem to indi- 

 cate some particular combination of hereditary units is very 

 interesting. It confirms the conviction of the writer that much 

 more work is needed in this field before the precise manner of the 

 inheritance of wildness and savageness in mice can be definitely 

 stated. However, from this study it seems that the two be- 

 havior-complexes in question are the result of several different 

 inheritance factors which follow the Mendelian rules. 



14. Three female wild mice were found which possessed the 

 "singing" property. No male was obtained which had this 

 characteristic. This "singing" did not appear in any of the 

 offspring to the third generation. It is evidently not inheri- 

 table, and quite possibly is a characteristic peculiar to females. 

 The phenomenon seems to be associated in some way with the 

 birth of young, and probably is caused by some structural defect 

 or a diseased condition of the vocal organs. 



BIBLIOGRAPHY 



G ALTON, Francis. 



1869. Hereditary genius, an inquiry into its laws and consequences. 

 London, pp. 390. 



1875. A theory of heredity. Contcrnp. Review, xxvii, pp. 80-95. 

 Lee, Henry. 



1878. Singing mice. Popular Science Monthly, xiv, pp. 102-105. 

 G ALTON, Francis. 



1889. Natural inheritance. London, pp. 259. 

 Ball, W. P. 



1890. Are the effects of use and disuse inherited. London, pp. 156. 

 Collins, F. H. 



1891. The diminution of the jaw in the civilized races, and effect of disuse. 

 London, pp. 16. 



