than a few seconds at a time. Most of their time, when they are first
taken from the nest, is spent in trying to maintain or regain an upright
position. The hair is now easily visible, and the skin begins to have a
white appearance as a result.

_Seventh day_. Although they are strong enough to move about the nest
readily, none of the young has attempted to leave the nest. They huddle
together in the middle of it for warmth. The epidermal scales, which have
increased in number since the third day, are dropping off rapidly. Contact
with the vibrissae or with the surface of the body, frequently calls forth
a motor reaction but neither light nor sound produces any visible change
in behavior. The black and white regions of the skin are sufficiently
definite now to enable one to distinguish the various individuals by their
markings. The mother was seen to dance repeatedly today, and she ate all
the food that was given to her.

_Eighth day_. A fold is plainly visible where later the eyelids will
separate. The black pigment in the skin has increased markedly.

_Ninth day_. The eyelids are taking form rapidly, but they I have not
separated. The body is covered with a thick coat of hair which is either
pure white or black. Standing on the four legs is still a difficult task.

_Tenth day_. To-day teats are plainly visible in the case of four of the
five individuals of the litter. Up to this time I had thought, from
structural indications, that there were three males and two females; it is
now evident that there are four females and one male. The external ear,
the pinna, is well formed, and has begun to stand out from the head, but
no opening to the inner portion of the ear is present. The eyelids appear
to be almost fully formed.