106 EVOLUTION OF THE HUMAN EYE 



structures. The caruncle, both in man and monkeys, has 

 become contracted up into a small elevation cut off from 

 any continuity with the skin of the face by the margins <>t* 

 the eyelids, which have completely closed round it, so that 

 it is entirely located in the lacrimal bay. That it really is 

 a vestige of the secreting odoriferous areas met with in 

 other mammals seems evident from its containing rem- 

 nants of all the constituents of such areas. The following 

 is the description of the structure of the caruncle given in 

 Quain's Anatomy: "Occupying the recess of the angle at 

 the border of the plica semilunaris is a spongy-looking 

 reddish elevation (caruncula lacrimalis), formed by a small 

 insulated portion of skin containing a few large, modified 

 sweat-glands, also a group of sebaceous glands which open 

 into the follicles of very fine hairs. There is further found 

 in it a small amount of plain muscular tissue (H. Muller) 

 as well as a few cross-striated muscular fibers." It is also 

 stated that in man, as in some animals, the caruncula lacri- 

 malis retains its connection with the skin at the inner canthus. 

 It is interesting to note in connection with this matter, that 

 the reduction of what must have been a large suborbital 

 pit to a comparatively small bald area at the inner canthus, 

 can be traced in the evolution of the horse. In the skull of 

 the modern horse no depression is found in the lacrimal 

 bone in front of the orbit for such a glandular structure. 

 In the fossil remains of the skulls, from the Pliocene epoch, 

 of the E. sivalensis of India and of the E. stenois of Europe, 

 traces of the depression or gland-cavity are met with, while 

 in the fossil skulls of the Hipparion, a three-toed horse from 

 Miocene beds, there is a very large depression in the bone 

 in front of the eye. 



In conclusion, I would claim that the changes in the 

 visual organs of mammals, produced by the adoption of 



