658 MAMMALIA. 



lemmings and marmots also belong. Like the hare (Lepus 

 timidus) and other species of the same genus, and like the 

 Picas or tailless hares (Lagomys)^ the rabbit has two pairs of 

 incisors in the upper jaw, while other Rodents have a single 

 pair. Therefore the genera Lepus and Lagomys are ranked 

 in the sub -order Duplicidentata, in contrast to all other 

 Rodents which form the sub-order Simplicidentata. 



With the rabbit's mode of life all are familiar. It is herbi- 

 vorous, and often leaves softer food for the succulent bark 

 of young trees ; it is gregarious and a burrower ; it is very 

 prolific, often breeding four to eight times in a year. It is 

 said to live, in normal conditions, seven or eight years. The 

 rabbit seems to have had its original home in the western 

 Mediterranean region, but it has spread widely throughout 

 Europe, and is now abundant in countries, such as Scotland 

 and Ireland, in which not many years ago it was quite rare. 

 Introduced into Australia and New Zealand it has multiplied 

 exceedingly, and has become a scourge. There are many 

 varieties of rabbit, some in isolated regions perhaps illustra- 

 ting the effect of segregation in fostering divergent types. 

 According to Darwin, the rabbits introduced early in the 

 fifteenth century into Porto Santo, an island near Madeira, 

 are now represented by a dwarf race of about half the normal 

 size, and these are said to be incapable of breeding with the 

 ordinary forms. But the varieties with which we are familiar 

 in the breeds of tame rabbits, illustrate variation under 

 domestication and the efficacy of artificial selection. 



External Appearance. 



The head bears long external ears which are freely mov- 

 able. The black patch at the tip of the ears in the hare 

 is either absent or very small in the wild rabbit. This 

 external ear is characteristic of most Mammals, and collects 

 the sound like an ear trumpet. In the rabbit it is longi- 

 tudinally folded, thin and soft towards its tip, firm and 

 cartilaginous at its base. The large eyes have eyelids 

 with few eyelashes, and a third eyelid or nictitating mem- 

 brane a white fold of skin lies in the anterior corner. 

 This third eyelid, which also occurs in Reptiles and Birds, 

 is present in most Mammals, and is of use in cleaning the 

 cornea. It is absent in Cetaceans, where the front of the 



