THE MOLE 



271 



With this large size (I have frequently 

 taken young fur-less Moles between three 

 and four inches long) is associated a cor- 

 responding muscular development ; but 

 the absence of any serviceable teeth 

 shows that the infants are as yet entirely 

 dependent on their mother, and it would 

 seem as if Nature had made careful 

 provision that they should not 

 leave the shelter of the nest before 

 their strength was sufficiently 

 developed to cope witli the 

 strenuous life before them. 



The very early stages of young 

 Moles present extremely interesting 

 features owing to the light which 

 they seem to throw on the evolu- 

 tion of ]\Ioles generally, and on the 

 probable extent of a Mole's powers 

 of sight and hearing. In the earliest 

 stage which I have been able to 

 examine, the eye is decidedly pro- 

 minent. It stands out from the side 

 of the head like a black pin-head, 

 and measures approximately '3 mm, 

 in diameter, the length of the head 

 from crown to nose-tip being, at 

 this time, about 5 mm. At a later 

 stage, when the head measures 

 10 mm. and the eye "5 mm., the 

 latter has a sunken appearance, 

 and is covered with a membrane 

 which persists until the young 

 Mole is ready to leave the nest. 

 When this occurs the eyes " open " 

 in the usual manner. 



In the dead adult Mole the eye 

 is so completely hidden by the fur 

 that the inexperienced may have 

 some difficulty in finding it. In a 

 living Mole, however, who is in good 

 fettle and vigorous (this is seldom the 

 case with Moles caught on the surface), 

 the fur stars round the eye to a breadth 

 of about 5 mm., and leaves the eye 

 clearly exposed as a dull-black ]nn- 

 head at the bottom of a greyish cone. 

 The Mole evidently possesses the power 

 of radiating the fur round his eyes at 

 will, and the presence of stiff, outstanding 

 bristles in their immediate neighbourhood 

 enables him to determine when such 

 radiation may safely take i)lace. In a 

 healthy Mole abov^e ground the fur is 

 always radiated. 



The external ear seems to pass through 



similar phases of degeneration. In the 

 quite early stage there are some signs of 

 a conch, but this soon contracts to a small 

 fleshy protuberance with a slit across it, 

 and, in the adult Mole, the ear-opening 

 can hardly be detected without shaving 

 the fur. 



It is further noticeable that the re- 



A MOLE'S ZIGZAG SUKiACK KLN. 



markable outward twist of a Mole's hands 

 is a comparatively late dexelopmi-nt in 

 the young Mole. 



All these facts point to the likelihood 

 of the Mole's e\-ident atlaptation to a 

 subterranean life ha\ing been gradually 

 acquired, and, although it would be 

 risky to base any conclusions as to his 

 powers of sight and hearing on merely 

 external features, the size and position 

 of his eye must, I think, preclude any 

 extended range of xision. The question 

 of his hearing is more difficult, as it can 

 be proved by experiment that the Mole 

 is extremely sensitive to sound-vibrations. 

 It may be found in future investigations 



