68 REPTILES AND BATRACHIANS. 



stop to consider their footsteps, but if surprised "immediately 

 conceal themselves." They "dig" deep holes to lie in, excavating, 

 no doubt, as other toads, with the hind limbs, and yet they 

 repose frequently in shallow water with only their noses exposed 

 to the air, which I never saw my toad do. Tate considers that 

 they display superior sense in ceasing to croak when disturbed, 

 but the same instinct which leads to concealment would also 

 induce silence. 



The tadpoles of the Natter-Jack are smaller than those of 

 Vvlgaris, and the metamorphosis is more rapid, lasting only six 

 or seven weeks ; but in a cold season this, no doubt, would be 

 prolonged, as we find to be the case throughout the class. The 

 generic characters are of course the same as Vulgaris. The 

 specific features are " Hind limbs short ; toes webbed at the base ; 

 no maxillary teeth ; crown without bony ridges ; snout short and 

 blunt ; first finger not extending beyond the second ; the male with 

 a vocal sac ; tympanum small, and not very distinct." 



J3. calamita has the same kind of skin as Vulgaris, the warts being 

 even more prominent, but the skin appears to me to be more 

 moist, like the frog's, and not normally dry, as in the common 

 toad. Its eyes are also prominent, said to be even more so than 

 in Vulgaris. You may, however, observe an individual in which 

 they are not nearly so prominent, perhaps due to a retractor 

 muscle, as in the frog, but of this I cannot speak with certainty. 

 It is very certain, however, that when closed, the eyes of both are 

 only very slightly prominent, being almost level with the surround- 

 ing parts ; and this retraction of the eyeballs during hibernation 

 is a noteworthy protection to them. The same method of 

 breathing as in the rest of the Batrachians may be observed ; a 

 sort of throbbing or continuous pulsation in the throat caused by 

 swallowing air. In the very small nostrils at the end of the 

 snout, in both toads, you may discern action likewise. The 

 nostrils are furnished with a valve to open and close at will ; and 

 under alarm or excitement this tiny valve acts with a rapid 

 nervous motion, opening and closing like an eyelid blinking; 

 only the valve is below and c'oses upwards, like the nictitating 

 membrane of the eye. The effect is very remarkable. When 

 disturbed during hibernation though at the moment the breathing 

 may be hardly perceptible the throbbing of the throat and the 

 action of the nostrils begin almost immediately ; while the 

 creature extends its limbs in a helpless manner, and then you see 

 the eyelids working, the nictitating membrane being the last to 

 recede and expose the eyeball, which by degrees assumes its 

 usual prominence. 



