92 



PROCEEDINGS OF THE ACADEMY OF 



V. 



[1893. 



The size and shape of the globular lens in the " telescope-eyed " 

 race is not appreciably different from that of the other races with 

 smaller eye-balls. It would therefore, seem impossible for the 

 image formed by the lens of a distant object in the "telescope 

 eyed " race, to be thrown upon the retina at all, consequently the 

 condition is one of near-sightedness, or of an optical adjustment for 

 very near objects. The conditions of life of these races, in small 

 tanks or aquaria, where they are bred under conditions of the great- 

 est protection from man, would in their restricted quarters actually 

 foster the development of near-sightedness, and any variations in 

 that direction would actually tend to be preserved. There is a con- 

 dition of disuse also to be taken into account in this process, since 

 these fishes no longer need their eyes with which to watch the 

 approach of their enemies, but only to look out for their food, 

 which is supplied to them by their human friends and protectors. 

 To what extent this factor has been of service in altering the shape 

 of the eye-balls, it is of course, as yet, impossible to state. The pre- 

 ceding table V, however, makes the gradual passage from the hyper- 

 metropic or flat eye of the normal race to that of the myopic or long 

 eye of the " telescope-eyed " race sufficiently obvious as the series of 

 measurements given of the eye-balls of the different races proves. 



The fact that a race of fishes may become myopic, as would seem 

 to be indicated by the foregoing data, is most surprising, and affords 

 a case parallel in some respects with that of the human race itself; 

 but in the case of these fishes the myopic tendency has probably 

 been further developed by the intentional selection of myopic indi- 



