Mr Hecvpe, Notes on the Proportion of the Sexes in Dogs. 129 
working, not without success ; and I hold that either quantita- 
tively or, more probably, qualitatively this is true. 
Of the various other agencies which it is claimed affect the 
proportion of the sexes born, such as in-breeding, cross-breeding, 
age, climate, temperature, &c. ; such power as they have, and I 
think there is sufficient evidence to show they are potent agencies, 
must be exercised either as a selective agent on the ova and 
spermatozoa, while within the generative glands of the parents, 
or as a purely destructive agent on the freed products of these 
glands. As selective agents these forces may act directly on the 
ovarian ova or indirectly affect them by modifying the vitality 
of the whole generative gland, making it thus more or less 
capable of assimilating the nutriment with which it is supplied. 
By these means ova requiring an excess of, or a certain quality of 
nutriment, will have their needs supplied or they will degenerate ; 
those most easily brought to maturity will ripen while others 
will fail to do so ; the special vitality of some ova will cause them 
to thrive, certainly at the expense of and probably on, their less 
active neighbours. 
The variation which exists in the physiological capacities of 
the adult male and female is surely represented in the sexual 
ovum. The marked difference in the death rate of males and 
females during famines, for instance (Lewis Mclver, Madras 
Census Report, 1881, vol. 1, 1883), may well be reproduced among 
male and female ova in the ovary when that organ is subjected 
to homologous conditions ; and such conditions may certainly be 
brought about in consequence of the active participation of one or 
other or many of the extraneous forces already alluded to. 
Thus, so far as this portion of the subject is concerned I am 
disposed to maintain : 
(1) that through the medium of nutrition supplied to the 
ovary, either by the quantity or by the quality of that nutrition, 
either by its direct effect upon the ovarian ova or by its indirect 
effect, a variation in the proportion of the sexes of the ova pro- 
duced, and therefore of the young born, is effected in all animals 
in which the ripening of the ovarian ova is subject to selective 
action ; 
(2) that when no selective action occurs in the ovary the 
proportion of the sexes of ovarian ova produced is governed by 
laws of heredity. 
With this very brief outline of my interpretation of the 
evidence before me regarding this section of a most intricate 
subject I must here content myself. 
in the following pages are treated various breeds of dogs and 
indications are given of the exercise of certain forces which appear 
to affect to some extent the proportion of the sexes produced. 
