THE RABBIT 419 



tail is conspicuous, and this, though no doubt it enables an 

 enemy to follow the fugitive, has probably advantages to the 

 species in guiding and warning other members of the society. 

 The head is separated from the trunk by a distinct neck, a 

 feature which we have not met with in the dogfish or frog. 

 The long external ears or pinna, are another new feature. 

 The eyes have movable upper and lower lids with a few 

 eyelashes, and a small third eyelid lies as a white membrane 

 in the inner corner and is used in cleaning the cornea. 

 This eyelid is rudimentary in man. The nostrils are two 

 oblique slits at the end of the snout, and lead internally 

 into the pharynx. We have seen that in the dogfish the 

 nostrils do not open internally and in the frog they open 

 into the front of the mouth. The upper lip is a "hare 

 lip," cleft in the middle, the cleft being continuous with 

 the nostrils and exposing the great front teeth. On the 

 sides of the snout and round the eyes there are strong 

 tactile hairs or vibrissa which correspond to the so-called 

 " whiskers " of the cat. There is no cloaca, the anus and 

 urinogenital openings being separate, and the latter in front 

 of the former, in the male on the end of a penis, in the 

 female within a slit-like vulva which contains in front a 

 small clitoris corresponding to the penis. Beside the penis 

 in the male lie the scrotal sacs, into which the testes of the 

 adult descend, but there is no hanging scrotum. Along 

 the breast and belly of the female there are four or five 

 pairs of teats on which open the milk glands of the mamma, 

 which we meet here for the first time. At the sides of the 

 anus are a pair of hairless depressions, into which open the 

 ducts of the perineal glands, to whose secretion is due the 

 peculiar smell of the rabbit. The limbs have the same 

 general shape as those of the frog and other land vertebrates, 

 being of the type known as pentadactyle (p. 40), though in 

 the rabbit, while the fore-limbs have five digits, the hind- 

 limbs have only four. The digits end in horny claws. 

 The fore-limbs are shorter than the hind-limbs, and in 

 running the animal does not tread upon the whole sole of 

 the foot, carrying the heel above the ground. 



The closely related Common Hare diners from the 

 rabbit in its greater size, the greater length of the hind- 

 limb, the black tips of the very long ears, the absence of 



