402 



SCIENCE 



[N. S. Vol. XLI. No. 1054 



the tendency of animals, the tendency of the 

 ancestors for three or more generations 

 should! be known. It must also be recalled, as 

 explained above, that the third factor " C " in 

 the female reduces the difference between the 

 ratio numbers of her male and female des- 

 cendants. As a result of this, the difference 

 between the number of males and females con- 

 sidering only mother tendency is smaller than 

 the difference between males and females in 

 the light of only the father tendency. A 

 male has a male tendency or a female tend- 

 ency and always maintains it, whereas the 

 female has a born male or female tendency, 

 but in addition to this she has a second tend- 

 ency to change her sex tendency from litter to 

 litter. The number of males and females 

 derived from the second generation was as 

 follows : 



I. Descendants of males whose fathers had 

 a male tendency mated with mixed females; 

 39 males to 54 females, i. e., 41.94 per cent, 

 males to 58.06 per cent, females (sex ratio 

 72.20). 



II. Descendants of males whose fathers 

 had a female tendency mated with mixed fe- 

 males; 42 males to 23 females, i. e., 64.61 per 

 cent, males to 35.39 per cent, females (sex 

 ratio 182.60). 



III. Descendants of males whose mothers 

 had a male tendency mated with mixed fe- 

 males; 64 males to 53 females, i. e., 54.Y0 per 

 cent, males to 45.30 per cent, females (sex 

 ratio 120.83). 



rV. Descendants of males whose mothers 

 had ;a female tendency mated with mixed fe- 

 males; 12 males to 13 females, i. e., 48 per 

 cent, males to 52 per cent, females (sex ratio 

 92.30). 



V. Descendants of females whose mothers 

 had a male tendency mated with mixed males ; 

 13 males to 18 females, i. e., 41.94 per cent, 

 males to 58.06 per cent, females (sex ratio 

 72.22). 



VI. Descendants of females whose mothers 

 had a female tendency mated with mixed 

 males; 51 males to 43 females, i. e., 54.25 per 

 cent, males to 45.75 per cent, females (sex 

 ratio 118.60). 



VII. Descendants of females whose fath- 

 ers had a male tendency mated with mixed 

 males; 38 males to 36 females, i. e., 51.38 per 

 cent, males to 48.62 per cent, females (sex 

 ratio 105.55). 



VIII. Descendants of females whose 

 fathers had a female tendency mated with 

 mixed males; 33 males to 37 females, i. e., 

 47.15 per cent, males to 52.85 per cent, females 

 (sex ratio 89.18). 



These figures show that in the sons the 

 tendency received from the father is stronger 

 than that coming from the mother, while in 

 the daughters the opposite is true. 



When one examines the descendants of ani- 

 mals whose fathers had a male tendency and 

 mothers a female tendency, a higher difference 

 in the relative number of males and females is 

 found than from those cases in which the 

 fathers alone had a male tendency. Twenty 

 descendants of such male animals (father 

 male tendency and mother female tendency) 

 mated with mixed females consisted of four 

 males and sixteen females, i. e., 20 per cent, 

 males and 80 per cent, females (sex ratio 

 25.00). From the females of the same type 

 (father male tendency and mother female 

 tendency) mated with mixed males, 29 males 

 and 15 females were derived, i. e., 65.90 per 

 cent, males to 34.10 per cent, females (sex 

 ratio 193.33). 



From the second-generation males whose 

 fathers had a female tendency and whose 

 mothers show a male tendency when mated 

 with mixed females were derived 32 males 

 and 15 females, i. e., 68.08 per cent, males to 

 31.92 per cent, females (sex ratio 213.33). 

 From the females of the same type (father 

 female tendency and mother male tendency) 

 mated with mixed males were derived 6 males 

 and 13 female descendants, *'. e., 31.58 per cent, 

 males to 68.42 per cent, females (sex ratio 

 46.15). 



Should one select males whose fathers had 

 a female tendency and whose mothers had a 

 male tendency and mate these with females 

 whose fathers had a male tendency and whose 

 mothers had a female tendency, a higher dif- 

 ference in the relative number of males and 



