In such cases the most probable solution seems to be, that the habit was at first acquired by practice at a more advanced age, and afterwards transmitted to the offspring at an earlier age.

But the young kangaroo is said not to suck, only to cling to the nipple of its mother, who has the power of injecting milk into the mouth of her helpless, half-formed offspring.

On this head Mr.

Mivart remarks: "Did no special provision exist, the young one must infallibly be choked by the intrusion of the milk into the wind-pipe.