Mr Hecipe, Notes on the Proportion of the Sexes in Dogs. 145 
This breed then is specially adapted for checking the general 
result given above and I have set it forth in Table IX. 
Table IX. 
Schedule Returns. Bloodhounds, gestation and sex of pups. 
Days of 
gestation 
Dogs per 
100 bitches 
Litters 
Pups per 
litter 
( 1 ) 53—61 
125-64 
9 
9-7 
( 2 ) 62—65 
138-46 
9 
6*8 
( 3 ) 66—69 
157-14 
4 
9-0 
Here is a very striking confirmation of the view advanced. 
The returns of the pups per litter in Tables VIII and IX do 
not indicate that the size of the litter has anything to do with 
prolonged gestation ; the litters produced both in divisions (1) and 
(3) in each of these tables are bigger than those in division (2), 
the normal gestation period, so it does seem as if the excess of 
male embryos in the uterus is directly responsible for the delay 
in parturition. 
I do not of course maintain that the length of gestation has 
any influence whatever on the sex of the young born, these 
results only show the tendency to prolong gestation when an 
excess of male embryos are present in the uterus. 
The association of a longer gestation period with the produc- 
tion of an excess of males may be regarded as evidence either 
that male embryos require a longer uterine life for their full 
development or that they are born, when possible, in a more 
advanced condition than the females. This is a question of 
considerable interest in relation to the physiology of breeding, 
and also regarding various sexual differentiations. 
Another point of interest with regard to Table VIII is that 
whereas 20 litters of Large dogs (18'35 0 /« of the whole) and 49 
litters of Terriers (29°/o) have a shorter gestation than normal, 
8 litters of Large dogs (7‘34°/o)> and 7 litters of Terriers (4T4"/o) 
experience a longer gestation than normal. 
Thus, while on the one hand abnormally short gestation is 
more usual than abnormally long gestation for both classes of 
dog, the proportion of Terriers is greater than that of Large dogs 
for short gestation, and the proportion of Large dogs greater 
than that of Terriers for long gestation periods. 
