322 Adaptation to Environment 



kept at the temperature of o° for a month or more 

 without giving rise to blind animals. Occasionally 

 such rudimentary eyes were also observed when eggs 

 were kept in a solution containing a trace of KCN. 

 Stockard has succeeded in producing cyclopean eyes 

 in Funduliis by adding an excess of magnesium salt 

 to the sea water in w^hich the eggs developed or by 

 adding alcohol, and McClendon has confirmed and 

 added to these results. 



The writer tried repeatedly, but in vain, to produce 

 Fundulus with deficient eyes by keeping the embryos 

 in the dark. Sperm and egg were not allowed to be 

 exposed to the light yet the embryos without exception 

 had normal eyes. 



F. Payne raised sixty-nine successive generations of 

 a fly Drosophila in the dark, but the eyes and the re- 

 action of the insects to light remained perfectly normal. 



Uhlenhuth has recently demonstrated in a very 

 striking way that the development of the eyes does 

 not depend upon the influence of light or upon the 

 eyes functioning. He transplanted the eyes of young 

 salamanders into different parts of their bodies w^here 

 they were no longer connected with the optic nerves. 

 The eyes after transplantation underwent a degenera- 

 tion which was followed by a complete regeneration. 

 He showed that this regeneration took place in com- 

 plete darkness and that the transplanted eyes remained 

 normal in salamanders kept in the dark for fifteen 



