2 Bruton, Note on the Eye of the Mole. 



dissection of the mole's eye, in which it is stated 

 that " notwithstanding the small size of the eye of 

 the mole, its appearance in foetal development is early ; 

 thus in a foetus recently examined the length of which 

 was about ^ inch the eyes were distinct ; they were visible, 

 conspicuous in the naked face, not much smaller than 

 those of the adult, and but little different in appearance. 

 The diameter of each was about -^-^ inch." 



The chief points noted in the dissection of the eye of 

 the adult mole were, briefly : 



1. There is no orbit : the eye lies immediately beneath 



the skin, with no bony protection whatever. 



2. There are no eyelashes, and the presence of eyelids 



is doubtful. 



3. One muscle only was found — an abductor. 



4. The aperture in the skin was ^V i^^^h in diameter : 



eyeball 2^5- inch in diameter : iris, dark brown : 

 pupil, circular : lens, yig inch in diameter : 



5. Traces of aqueous and vitreous humour were found. 



6. As the eyes are very low down and far forward, 



the optic nerves are unusually long. 



Darwin has this remark upon the subject {Orig. Spec. 

 6th ed., p. 1 10) : — " The eyes of moles and of some burrow- 

 ing rodents are rudimentary in size, and in some cases are 

 quite covered by skin and fur. This state of the eyes is 

 probably due to gradual reduction from disuse, but aided 

 perhaps by natural selection .... As frequent inflam- 

 mation of the eyes must be injurious to any animal, and 

 as eyes are certainly not necessary to animals having 

 subterranean habits, a reduction in their size, with the 

 adhesion of the eyelids and growth of fur over them, 

 might in such case be an advantage, and if so, natural 

 selection would aid the effects of disuse." 



Mr. Adams refers to the report that when a mole is 



