248 ROYAL SOCIETY OF CANADA 
to innate vigour, one of the two birds in the nest may make a sudden 
advance, as was noted in the dog, in which case the same result as just 
referred to follows. 
There are many signs of development that appear progressively, 
such as changes in the shape of the skull and beak, the method of hold- 
ing the head, the relative proportion of parts, ete. ; but upon the whole 
the rate of feathering is a fairly good guide to progress, both physical 
and psychic. 
Though differences between the mature forms of varieties of pigeons, 
so pronounced as regards physical form, less so psychically, but still real 
and always present, are obvious to even a superficial observer, it is inter- 
esting to note that even at an early date such differences do appear. To 
illustrate: the dragoon is a bird of a very bold appearance, and as com- 
pared with many varieties, is somewhat wild. It has been spoken of as 
the “game bird” of the pigeon family. Such characteristics are mani- 
fest in the young before they are twenty days old. They peck sooner 
and more vigorously in the nest. They are shyer of approach, ete. 
This cannot be explained by a more rapid development, for several 
other varieties mature sooner than they do. 
Changes in the colour of the iris are as significant, it would seem, as 
in mammals. 
SOME CONCLUSIONS. 
Pigeons, when hatched, and for the first day or two, keep their eyes 
mostly closed, though the eyelids are not actually united at birth. 
They are both blind and deaf when they first emerge from the shell, 
and for a certain period afterwards. 
Perfection of hearing and vision are gradually but rapidly acquired- 
Taste and smell cannot be demonstrated at birth, but can be shown 
to exist some days later. 
From the first tactile sensibility and capability for painful sensations 
exist in exquisite development. 
Pigeons, even more than mammals, seem to be sensitive to heat and 
cold. 
The sense of support is very fully developed almost or quite from the 
beginning. 
Voice is present in a few days after hatching. 
Motor co-ordinations peculiar to birds and the power of recognizing 
their own nest, parents, etc., are gradually but well developed. 
Physical changes peculiar to this group of birds, and with modifica- 
tions for each variety, occur at fairly definite periods, are closely 
related in time and are probably in some way bound up with psychic 
changes. 
