SETON — BREEDING OF DEERMICE 
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Twice I saw him in the act; it is done with one front paw striking 
down on any near object, so fast that one sees a mere haze of paws for 
the half second that it lasts. (Later I had a male that drummed a little 
with his tail.) The httle female made a hammering as she scratched 
herself with a hind foot; but I have not yet seen a female make the 
drumming.^"(Later, I kept two females for some weeks, and never 
once heard them drum.) 
These mice often squeak shrilly while fighting with each other. 
(Later I noted one that gave off a succession of squeaks when caught 
in a trap.) These observations on the voice are of interest since M. A. 
Walton, who first recorded the drumming of these mice, says they are 
Fig. 1. Exteen AL Genitals of Peromyscus leucopus noveboracensis. 
Male. 
One and one-half times natural size. 
completely dumb.^’ It is always dangerous to say that an animal 
with vocal organs is dumb. In this case, the voice may be so high 
pitched that only very young, or very sharp ears can hear it. 
June Jf.. To-day one of the mice, the younger female, is obviously 
near bringing forth young. 
June 9. The young mice, 3 in number, were born either yesterday 
or the day before, so that gestation apparently is 23 days. One of 
them, measured June 10, was in body liV inches long, tail inches. 
When it was left at the door, the mother nosed it, whiskered it, then 
carried it back to the nest. When they were 11 days old, I chanced 
to disturb the mother mouse. She ran out with two of the young 
attached to her inguinal teats. Although she ran fast, turned, twisted, 
climbed the bars, carried stuff to the nest and rebuilt it, they hung on, 
bumping along with every inequality. Later I saw her remove one of 
