Sex Ratios in Pigeons. 
487 
rows 7 and 8, in which the proportion of total males to total females is 
nearly 108 : 100, we find that of the 589 known A-eggs, 299 pro¬ 
duced males and 290 females. This is a ratio of only 103 : 100; 
in other words, the excess of males from A-eggs is slightly less in this 
case tha?i normal for both eggs. As would be expected, we find a 
correspondingly -larger proportion of males to females from B-eggs, 
namely 289 males to 256 females (rows 9 and 10), or 113 : 100. 
This result confirms that which Cuenot obtained with small numbers, 
to the effect that there is no basis in fact for the belief that the A-egg 
more often produces males and the B-egg females. 
Considering now only those cases in which the sexes of both 
squabs were determined, we note (rows 11 and 12) that there weie 
284 bisexual broods to 302 unisexual, and that of the latter 149 
consisted of two males and 153 of two females (rows 13 and 14). The 
expectation, if we assume that sex is determined by chance, would be 
equality in both instances. In the ratio of bisexual to unisexual 
broods the chances are about even that the divergence from equality 
would be as great as 'that observed, with the odds very slightly 
against it.* On the other hand the ratio of 149 broods ‘both males’ 
to 153 broods ‘both females’ is well within expectation.! While, 
thei efore, the numbers of the bisexual and unisexual broods are rather 
divergent, they are not so far apart as to demand any other ex¬ 
planation than that of a chance result, and for practical purposes 
the male as compared with the female broods may be considered as 
- 
equal. It happens that there are four more of the latter than of the 
*Ratio obtained, 284 : 302. 
Deviation from equality — 9. 
Probable error (0.07449 'J n p q; n, number of individuals, p and q, proportions expected in each 
class, in this case J4 in each) = 8.1638. 
Deviation 
Probable error 
The odds against a deviation as great as 9 are accordingly 1.18 to 1 
(Pearl and Miner, 1914). 
tRatio obtained — 149 : 153. 
Deviation = 2. 
P. E. = 5.80. 
-2_ — 0.34. 
P. E. 
