FECUNDITY OF KATS. 
167 
tells me of one case he heard of, wherein tv/enty-three were 
found. Nevertheless, I am satisfied from personal expe- 
rience, that the average number ranges between eight and 
fourteen at a litter ; and that these large numbers are mat- 
ters but of rare occurrence. 
In the next place, I am informed that rats will have six, 
seven, and even eight nests of young in the year, and this 
for three or four years running ; that the young will breed 
at three months old ; and that there are considerably more 
females than males. 
In order that I may not leave the smallest room for doubt 
or dispute, I propose laying down my calculations at some- 
where about one-half In the first place, I will say four litters 
in the year, beginning and ending with a litter ; thus making 
thirteen litters in three years. Secondly, to have eight 
young ones at a litter, half male and half female ; and, 
thirdly, the young ones to have a litter at six months old. 
At this calculation I will take one pair ; and at the end of 
three years what do you suppose will be the amount of living 
rats ? why, no less a number than 651,050 ; that is, includ- 
ing the father, mother, children, grandchildren, great-grand- 
children, &c. 
The enormous number of 651,050 living rats springing 
from one pair in three years, appears a thing almost incre- 
dible. Yet it is an arithmetical fact. Nevertheless, for 
the satisfaction of those who may feel curious in the matter, 
and have an inclination to investigate for themselves, I will 
give the round numbers of young, each littering, as they 
transpire. Therefore, suppose we commence with Lady-day 
1856, and finish on Lady-day 1859, then we shall find the 
following to be the result : — 
First litter, 8 ; second litter, 8. 
In the third littering, the first young ones being then six 
months old, the four females, with their mother, will have a 
litter each, which, together, will number 40. Thus will they 
fall in to the finish : — 
Fourth littering, 72 ; fifth, 232 ; sixth, 520 ; seventh, 
1,448; eighth, 3,528; ninth, 9,320; tenth, 23,432; eleventh, 
60,712; twelfth, 154,440; thirteenth, 397,288. Now add 
all these together, and the number will be 651,050. 
