Mr Heape , Notes on the Proportion of the Sexes in Dogs. 149 
bitches is 11749. Nearly 50% of these pups are Greyhounds 
(17838), with 118’5 dogs per 100 bitches, and no other breed 
dealt with is represented in anything like the same numbers ; 
Collies with 6777 pups are the nearest and the proportion of 
dogs per 100 bitches in this breed is 118T9. 
Apart from Greyhounds the returns deal with a variety of 
breeds and if details of all Large dogs are abstracted therefrom it 
is seen that of the total pups recorded (11846) 6413 are dogs and 
5433 bitches, i.e. there are here 118 , 04 dogs per 100 bitches. 
Thus there is a very remarkable approximation in the proportion 
of the sexes produced by Greyhounds and Collies or by Grey- 
hounds and the other Large dogs, taken as a whole, with which 
we have dealt. 
The Terriers, taken as a whole, give a somewhat different 
result. Of these we have a total of 7183 pups, 3829 dogs, and 
3354 bitches, giving 114T6 dogs per 100 bitches. A difference of 
four is not a wide variation, especially when the numbers dealt 
with are considered. Still there is this difference and I am 
disposed to think a more extensive series of data will demonstrate 
that there is a distinct racial variation in the proportion of the 
sexes produced by these two classes of dogs. 
Again there is wide diversity in the results obtained for 
different breeds of both Large dogs and Terriers. The numbers 
dealt with are too small for safe generalisation, but the results are 
so marked in several cases that I believe racial variation will be 
found to exist between different breeds as well as between dif- 
ferent classes of dogs. 
Greyhounds. The data supplied to Darwin for Greyhounds 
gave 110T males per 100 females during the years 1858 — 1868, as 
against 118’5 in the above records 1886 — 1892. It is possible that 
in-breeding in these later years has had some effect in the direction 
of an increase in the proportion of dog pups born, but in the 
absence of assurance that all pups born were recorded by Darwin’s 
informants, it seems probable that the difference is chiefly due to 
neglect of this source of error. 
The returns now presented show the proportion of dogs born 
each year (Table I) and the proportion born per month for all 
these years jointly (Table II). 
It is seen that most Greyhounds are born during certain 
months, March to June, and that the proportion of the sexes born 
then varies but little. 
During every month in a series of years there is a prepon- 
derance of dog pups born, but during October to December, when 
the fewest pups are born, the proportion of dog pups is at its 
highest. The conclusion is drawn that conception during August 
to November is especially favourable to the production of dog 
