THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 167 
physical. It is not easy to make perfectly evident in a 
diary the extent to which individuality is shown, but 
even in the blind period it exists, and to a close 
observer, familiar with dogs, and the particular breed 
being studied, it shows itself in a variety of ways, often 
it may be difficult to describe in words. Sometimes, 
when but a few weeks old, a puppy foreshadows his 
future in an unmistakable way. 
PERIODS OF DEVELOPMENT.—A study of the diary 
will show that the two great periods are: that before 
the eyes are open, and that succeeding this one. The 
time between the opening of the eyes, and the establish- 
ment of real vision and hearing, constitutes a transition 
or intermediate period. 
Development is very slow in the first period, and 
existence almost a vegetative one, yet not wholly so, for 
by the skin, the muscular sense, to some extent, by taste 
and smell, by visceral sensations, etc., the animal’s 
nervous centres are being modified. 
The intermediate period is marked by a considerable 
advance, though slow, as compared with the progress 
made within the next few days. 
The period between about the 17th and the 45th day 
is that of greatest importance in the life of the dog. 
After that there is constant improvement, from ex- 
perience, up to the 60th day, and this is well marked— 
more so than at any later time, but it is not of equal 
importance with that preceding. 
These periods glide into one another, and many others 
might be interpolated, but I desire to avoid artificiality, 
which is sure to result from the attempt at numerous 
divisions of any kind. 
There is not the sharp line of difference between the 
dog and other animals, before the eyes are opened and 
afterwards, which some writers would have us believe, 
though between the animal, when it can neither see nor 
