Chap. II.] EXTERNAL CHARACTERS. n 



line (I. .), the scales are peculiarly modified, so as probably to 

 minister in some way to special sensation. The barbule (b.) 

 beneath the chin is probably an organ of touch. The eyes are 

 large, and have no definite eyelids. There is no external 

 aperture of the ear, nor is there, as in the frog, any visible 

 tympanic membrane. 



3. The Rabbit. The wild rabbit (Lepus cuniculus) frequents 

 furzy sandy heaths, taking shelter when disturbed in deep 

 burrows, which it digs in the sand. In wet soils, instead of 

 digging burrows, it forms "runs "or galleries in the matted 

 vegetation. Its food is green vegetable matter, especially the 

 young shoots of the furze. 



The rabbit begins to breed at the age of six months, and has 

 several litters of from three to nine young in the year. At this 

 rate a single pair of rabbits might, at the end of about five 

 years, look round with pardonable pride on a colony of some- 

 thing like a million descendants. The mother forms a special 

 chamber in which the young are born and suckled. At birth 

 they differ considerably from the adult. The head is much 

 larger, the ears comparatively short, the tail a respectable length, 

 and the fore and hind limbs of about equal size. They have a 

 much more average mammalian appearance than the adult ; 

 specialization setting in as they grow up. They are suckled 

 for a fortnight or so, and are adult in five or six months. 

 During that time the rate of growth of the trunk is greater 

 than that of the head ; that of the hind-legs much greater than 

 that of the fore-legs. The ears grow very fast, and the tail 

 hardly at all : the former tend to droop, while the latter 

 acquires its characteristic upward curve. In all this there is 

 something more than growth there is development. But there 

 is no metamorphosis. 



In the adult rabbit there is a distinct head, pretty well 

 marked off into a facial region in front, and a cranial region 

 behind. The neck is short, but distinct. The body is stout and 

 slightly elongated, and divided into a thoracic region anteriorly, 

 and an abdominal region posteriorly. The sides of the thoracic 



