698 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 some- 

 times ranked as Duplicidentata, in contrast to all other 

 Rodents (Simplicidentata). 



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

 ivorous, and often leaves softer food for the succulent bark 

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

 prolific, frequently breeding four 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 regions, such as the High- 

 lands of Scotland, in which, a few generations ago, it was 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 illustrat- 

 ing 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 movable. 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 longitudinally folded, thin and soft towards 

 Its tip, firm and cartilaginous at its base. The eyes have 

 two eyelids with few eyelashes, and a third eyelid or nicti- 

 tating membrane a white fold of skin in the anterior upper 

 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 eye is bathed by the water, and it is rudimentary 

 in man and monkeys, where its absence is compensated for 



