1903.] 



Observations on the Sex of Mice. 



33 



Part T. — Generalisations. 



The first question as to which we are desirous of obtaining informa- 

 tion concerns the possibility of the male or female parent, in any- 

 particular instance, exerting a marked influence in the direction of a 

 preponderance of male or female offspring. In seeking an answer to 

 this question it is necessary to state that out of the total number 

 of 493 young produced in the course of our experiments, 258, or 52 "3 

 per cent., were of the male sex, and 235, or 47 '7 per cent., of the 

 female sex. 



Taking the buck's descendants first, we have the following 

 records : — 



«?• ?. 



. a 71 (48 per cent.) 77 (52 per cent.) 



§ 18 (66-5 „ ) 9 (33-5 „ ) 



y 28 (46-5 „ ) 32 (53*5 „ ) 



8 52 (57 „ ) 39 (43 „ ) 



* 25 (43 „ ) 33 (57 „ ) 



£ 6 2 



n 33 (66 „ ) 17 (34 „ ) 



e 7 6 



i 18(51 „ ) 17(49 „ ) 



k 3 



258 235 



The cases of £, and k may be left out of consideration, as the 

 numbers of their offspring are so few. Of the rest, oc and t closely 

 approach the normal, but ft, 8 and rj have male offspring in excess, in 

 connection with which fact it must be remembered that 8 was the son 

 of p. On turning to the record of /3, we find that in the case of 

 all five does with which he was mated, the male offspring was in 

 excess, and in the case of 8 also when put to five different does in 

 succession, more males were produced than females in every instance. 

 f] was put to seven does — five times males were in excess, once the 

 sexes were equal, while only once (with C 1,2,2,1 ) were there more 

 females than males produced, y and e on the other hand had female 

 offspring in excess of male to a rather marked degree, and in each 

 case the record is taken from more than fifty young. With y the 

 females were in excess of the males in four litters out of nine, while 

 in two others the sexes were equal, so that in only three out of nine 

 litters were there more males than females. In the case of e the 

 females were in excess in five litters out of nine, while in one other 

 the sexes were equal. In this case too there were more males than 



VOL. LXXIII. D 



