245 
i88o.] The Rate of Animal Development . 
sitters and nest-quitters ( nest-hocker und nest-fliichter ) , ac- 
cording as when hatched they remain helpless in the nest 
or are at once able to run about and seek food for them- 
selves. 
Davy, by the mouth of “ Ormther,” gives a very lame 
explanation of the fadt that the majority of birds cannot fly 
as soon as hatched. Before they can take flight they have 
to await not alone the growth of their, wing-feathers, but 
the simultaneous development of the muscles. The Rap- 
tores, Passeres, &c., are, as we have already seen, unable to 
walk as well as to fly. Does this inability depend upon the 
want of feathers ? The fadt that parent birds educate their 
young is clearly established by the interesting observations 
of Dr. C. Abbott.* 
In the case of birds of prey the process of education is 
somewhat prolonged, even after leaving the nest. It is 
thought by many that Deuteronomy xxxii. ; v. 11 , is a 
description of the manner in which eagles train their young 
to fly; “ stirring up ” the nest, i.e., shaking and disturbing 
it so ’as to compel the nestlings to leave their cradle ; 
“ fluttering ” over them and “ bearing them on her wings,” 
— that is to say, following and intercepting their downward 
movement, and aiding them to re-ascend. 
Thus we see that the condition of the young of the lower 
animals is after all analogous to that of the human infant. 
The child, indeed, is still slower in learning to walk than 
the kitten or the young ape, not because he has to learn in 
a different manner, but because the development of his 
muscles and joints is much more gradual ; because his head 
is relatively heavier; because he has to support himself on 
one pair of limbs only, thus rendering his base much nar- 
rower and his centre of gravity higher from the ground ; 
and because, as we have already pointed out in the case of 
the kitten, the hinder extremities gain strength more slowly 
than the anterior. 
Surely, therefore, the helplessness of the human infant 
can no longer be regarded as an exceptional phenomenon, 
and all conclusions based upon it by rhetoricians may be 
safely dismissed to dream-land, whence they came. 
* Quarterly Journal of Science, vol. vi., p. 361. 
