_Eleventh day_. There are no very noticeable changes in appearance except
in size, which continues to increase rapidly. They are able to regain
their normal upright position almost immediately when they happen to roll
over. The mother dances as usual.

_Twelfth day_. It appears to-day as if the eyes were about to open. The
ears are still closed, and there is no evidence of a sense of hearing.
They squeaked considerably when in the nest, but not at all when I took
them out to note their development. The mother stays outside of the nest
box much of the time now, probably to prevent the young ones from sucking
continuously.

_Thirteenth day_. One of the little mice came out of the nest box while I
was watching the litter this morning, and was able to find his way back
directly despite the lack of sight. The mice are still dependent upon the
mother for nourishment. I have not seen any of them attempt to eat the
food which is given to the mother. They are extremely neat and clean. I
watched one of them wash himself this morning. Each foot was carefully
licked with the tongue. There seems to be special care taken to keep the
toes perfectly clean.

_Fourteenth day_. An opening into the ear is visible to-day. When tested
with the Galton whistle, all five responded with quick, jerky movements of
the head and legs. They evidently hear certain tones. During the past two
days the ears have changed rapidly. In one of the females, which seems to
be a little in advance of the others in development, certain peculiarities
of behavior appeared to-day. She jumped and squeaked sharply when touched
and sprang out of my hand when I attempted to take her up. This is in
marked contrast with her behavior previously.