128 Mr Heape, Notes on the Proportion of the Sexes in Dogs. 
Although the causes which induce the degeneration of ova 
have not been surely demonstrated, I think it may unhesitatingly 
be accepted that nutrition plays a very important part therein ; 
but whether it exerts a selective action as regards sex, whether 
it affects the proportion of male or female ova which ripen, there 
is, so far as I know, no conclusive evidence. On this subject of 
nutrition and sex there is again a large literature which it is 
impossible to present fairly here. Most of it is written to show 
that the sex of the embryo can be governed by the nutriment 
supplied to the mother during gestation and with this section, 
for reasons already stated, we have nothing to do ; for the rest, 
almost all of it is based upon the supposed effects produced by 
the quantitative supply of nutriment presented to the mother. 
There is much confusion about the whole of this section of 
the subject. For instance, in support of the view, very generally 
held, that more nutriment is required for the production of 
females than for males ; it is argued that, as the adult female 
has greater capacity for storing nutriment than the adult male, 
this fact is evidence that more nourishment is required for her 
production. I think it is clear that the viviparous female has, 
broadly speaking, greater powers of storing nutriment than is 
possessed by the male. Her maternal functions require such 
special capacity and, though I will not give data here, I will add, 
there is conclusive evidence to my mind that she possesses it. 
But if it is so, that is no evidence that the ovum from which 
she is derived requires more nourishment for its development. 
Again, the greater difficulty experienced in rearing male than 
female children is attributed by some observers to the better 
nourished condition in which girls are born ; and many have 
argued, in one form or another, this is clear evidence that the 
mother needs an extra supply of nourishment to enable her to 
produce a girl. So far as this latter point is concerned perhaps 
the greater mortality among male infants is otherwise to be 
explained. But however this may be the point at issue is not 
affected thereby, for if nutriment has any effect at all upon the 
proportion of the sexes produced, it must be exerted on the ovum 
in the ovary ; that is to say it is the capacity of the mother to 
supply the ovary with nutriment which must be taken into 
consideration. Now it does not at all follow that a female with 
exceptional powers of assimilating and of storing nutriment, or 
that a mother especially capable of producing well-nourished 
offspring, gives birth to an excess of females ; indeed my own 
experiments indicate that the reverse, in many cases, is true. At 
the same time there are records of experiments which may, in my 
opinion, be interpreted to show that nutrition has a selective 
action on ovarian ova; it is on these lines I have myself been 
