324 



Mr. R. J. Lee on the 



[Apr. 28, 



No. 3S, p. 105) all the ordinary elements of the eye are found in Spa/ax 

 typhlus" 



Leydig, in his 1 Handbuch der Histologic/ has some important remarks 

 on the eyes of blind animals, and has described, in Muller's * Archives/ 

 1854, p. 346, the cellular structure of the lens of the Mole's eye, as pre- 

 senting the character of embryonic structure, from which he concludes that 

 the lens remains in its primitive embryonic condition. 



Mr. Solly's investigations were directed to the state of the optic com- 

 missures at the base of the brain. " In the Mole," he says, "in which the 

 optic nerves are so extremely minute that they have often escaped detec- 

 tion, and are by many authors described as entirely wanting, these com- 

 missural fibres are found distinctly crossing the base of the skull opposite 

 the usual situation of the optic commissure ; while the small black speck, 

 evidently the rudiment of the eye, is supplied by a minute branch from the 

 fifth pair" (p. 289, op. cit.). 



In Prof. Owen's work on the ( Comparative Anatomy and Physiology of 

 Vertebrates' (vol. iv. p. 246), the organ of sight, like that of smell, 

 is stated to be M wanting in a few mammals, the eyeball being reduced to 

 the size and condition of the ocellus in Amblyopsis, and to its simple 

 primitive office of taking cognizance of light, a filament of the fifth aiding 

 a remnant of the proper optic nerve. The Moles, especially the Italian 

 kind, Talpa cceca, and Mole-rats, exemplify this condition, in which, as in 

 Spalax txjphlus, the skin passes over the ocellus without any palpebral 

 opening or loss of hair." 



Mr. Herbert Mayo has given a similar description in his f Physiology,' 

 and has supplemented it by a drawing, in which the fifth nerve is repre- 

 sented as sending a filament directly to the globe of the eye, 



From the above enumeration of the views entertained by anatomists re- 

 garding the eye and optic nerve of the Mole, it is apparent that attention 

 has been directed by some to the eye in particular, and to the structures 

 intimately connected with it, while others have arrived at their conclusions 

 from examination of the interior of the skull and the optic region of the 

 brain. 



It remained therefore to ascertain the condition of the optic nerve in the 

 posterior part of the orbit, especially that portion of the nerve which lies 

 in the optic foramen, and thus endeavour to connect the appearances de- 

 scribed in the eye with those observed at the base of the brain. 



It is proposed to give an account of the dissection of the full-grown 

 Mole, in order to contrast the state of the eye, the optic nerve, and the 

 cranium with that which those parts present in the fcetal Mole, following 

 such an arrangement of the facts that the important points of difference 

 shall be apparent without separate comparison. 



The eye of the Common Mole presents the appearance of a minute black 

 and shining bead, closely attached to the skin of the head, and concealed 



