The kangaroos have now become familiar objects to all who visit our Zoölogical Gardens, or who are familiar with any considerable zoölogical museum. Their general external form, when seen in the attitude they habitually assume when grazing (with their front limbs touching the ground), may have recalled to mind, more or less, the appearance presented by-some hornless deer. Their chief mode of locomotion (that jumping action necessitated by the great length of the hind-limbs) must be familiar to all who have observed them living, and also, very probably, the singular mode in which the young are carried in a pouch of skin in the front of the belly of the mother. But "What is a kangaroo?"