EVOLUTION OF THE HUMAN EYE. 



INTRODUCTION. 



The influence of the environment in the production of 

 changes in the visual organs is a large and interesting sub- 

 ject—so large that it is only possible to attempt dealing 

 with a comparatively small part of it in this lecture. The 

 part most full of interest to this society must necessarily 

 be that which concerns the higher mammals. A study of 

 the morphology of their visual organs shows that there is a 

 very close resemblance between those of man and monkeys, 

 and some very wide differences between those of monkeys 

 and the lower mammals. The chief cause of these marked 

 changes is, I propose to show, to be found in the alteration 

 in environment produced by the adoption of arboreal life. 



Dr. Wood Jones 1 in 1915 delivered a lecture at the Royal 

 College of Surgeons "On the Influence of the Arboreal 

 Habit in the Evolution of the Reproductive System," and 

 I cannot do better than quote here the following passage 

 from his opening remarks : 



"No doubt the assumption of the upright posture has 

 done much in putting the finishing touches upon the evolution 

 of the human stock, but we must be careful to give it no 

 more than its real value. Long before the fashion of walk- 

 ing upright had been even foreshadowed in the crouching 

 gait of the half-finished product, a potent factor was 

 2 



