THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 159 
that there is a development of growling in sleep, 
growling when awake, barking (incipient as in older 
dogs) during sleep, probably in dreams, barking simply 
as an expression of surplus of energy, barking in 
wantonness, etc., all of which is, like the wagging of the 
tail, highly characteristic of different psychic states. 
All these modes of expressions are to be witnessed 
with precisely the same interpretation in older dogs at 
times, though, of course, generally the meaning of their 
barking and growling is more definite. But the puppy 
persists latent in the dog, just as does the boy in the man. 
DrEAMING.—Mature dogs do undoubtedly dream, 
and if one may judge by similar use of the voice and 
like general behaviour, puppies do also, Leaving out 
of the question the doubtful evidence of growling in 
sleep, the phenomena reported on the 35th day seem to 
point to dreaming, for the behaviour of the puppy is 
very similar to that of the mature dog. 
ANGER.—Much of the play of dogs is mimic fighting, 
even from the first, and 1 have noted on the 27th day, 
during play, a very brief but decided exhibition of anger, 
such as may occasionally be seen among mature dogs, 
or boys even of eight or nine years of age during rough 
play. For the moment anger rules, and the extent to 
which this is the case, and especially the length of time 
over which it lasts, depends greatly on the breed of the 
dogs. With terriers very early play at times becomes 
serious, and later it may so often become fighting that 
these dogs cannot always with safety be left together. 
In few respects do the different breeds show their 
characteristics, or at so early an age, as in this. For 
a very early case of anger (or was it a mere reflex ? ) 
see the record of the 17th day, and for a clear case the 
record of the terriers on the 30th day. 
Memory.—In a sense all impressions are remembered, 
z.e. the state of the nervous system, indeed the whole 
