PROBLEM OF CAVE BLINDNESS 249 



the rudimentariness may be in some cases imposed 

 on each individual generation, and the result of 

 peculiarities of nurture rather than of hereditary 

 nature. 



This is, of course, a matter for experiment, and 

 some data are already available. Thus, Ogneff 

 kept goldfishes for three years in absolute darkness, 

 taking care to give them plenty of room and plenty 

 of food. The result was total blindness; even the 

 rods and cones of the retina disappeared. We may 

 suppose, then, that if some goldfishes were washed 

 into a cave, they might become blind. It is likely 

 enough too (it ought to be tried) that their offspring 

 would show even greater degeneration of the eye, 

 being exposed to darkness from birth. If the 

 degeneration of the eye continued to increase after 

 the second generation (and this also should be 

 tested), a case would be forthcoming in support of 

 the theory that individually acquired modifications 

 may become in some measure part of the inherit- 

 ance. But the evidence of this is not as yet 

 forthcoming, and OgnefFs experiment should be 

 repeated by other experimenters and on other 

 fishes. 



It is a very instructive fact that the wan Proteus 

 from the caves, which shows no pigment in its skin, 

 becomes rapidly spotty and then dark-colored when 

 brought into the light. It responds like a photo- 

 graphic plate, and the eggs produced in the light 

 develop into dark-colored offspring. How slow 

 one should be to infer the absence of a potentiality 



