AND DESERTS 137 
In one respect, however, the kangaroo shows a very 
striking contrast to the ungulates. We have noted 
that among the swift ungulates the tendency is for the 
young to be born very fully developed, able after a very 
short period to run by the side of the parent. The 
consequent long period of gestation is dangerous to 
the mother, but has apparently been justified in the 
struggle for existence by the higher survival rate of 
the young. Further, as we may note readily among 
domesticated sheep, the young ungulate, when suck- 
ling, is not allowed by the mother to satisfy its appetite 
completely—it must never be so satiated as to be in- 
capable of flight. In the case of the kangaroo con- 
ditions are very different. The period of gestation is 
very short, and the young one is born in a very im- 
perfectly developed condition, incapable of sucking and 
quite incapable of voluntary movement. It is placed 
by the mother in the pouch with which she is provided, 
and attached to the teat. Milk is then pumped into 
its mouth, by the action of certain of the muscles of 
the mother. Owing to this abundant food, growth is 
rapid, and soon the young one is able to move and 
leave the pouch. It however always returns to it 
on an alarm, and is not able to care for itself 
till it is some eight or nine months old. The mother 
shows great devotion to her young, but if hard pressed 
by dogs she will throw the young one out of the 
pouch into the fern, thus relieving herself of a weight 
which diminishes her speed. The action has been 
variously interpreted. According to some authorities 
the chances are that the dogs will neglect the young 
one and continue to chase the mother, who, if she 
escapes, will return to pick up her ‘joey’. Others 
regard the action as equivalent to an abandonment of 
