144 EDUARD UHLENHUTH. 



months old, and all the structures, with the exception of the 

 sex organs, were perfectly developed. The retinas of these 

 transplanted eyes were found to be normal in every detail. 



In addition to the above I have a preparation of an eye of the 

 "light" series, which was preserved 3 1/4 years after trans- 

 plantation, at which time the sex organs were also fully developed. 

 According to Roux the eye of an amphibian should by that time 

 already have entered the functional period, as is believed to 

 have been proved in the case of the eye of the Proteus. Never- 

 theless, the old transplanted eyes were also found to be normal, 

 and the functional parts of the retina, viz., the rods and cones, 

 were present and well developed. 



The above results, namely, the permanent preservation in a 

 normal condition of transplanted eyes, prove beyond any doubt 

 that the so-called functional structures of the eye do not undergo 

 atrophy through inactivity, even if they are kept under extremely 

 unfavorable conditions and are deprived of all function and func- 

 tional stimulus. 



This fact alone is sufficient to show that atrophy from inac- 

 tivity, which is one of the fundamental postulates of Roux's 

 theory, is by no means a phenomenon of general occurrence 

 which takes place in all so-called functional structures perman- 

 ently deprived of functional stimulus, as was supposed to be 

 the case. 



As far as regeneration is concerned, the experiments mentioned 

 above only serve to show that regeneration in itself is indepen- 

 dent of function and functional stimulus. 



V. I am, moreover, able to demonstrate that the "quantity" 

 of the regenerative process in the eyes, viz., the rapidity of this 

 regeneration are not influenced by functional stimulus, viz., light. 



A certain number of animals (260 in all) of both the light 

 and the dark series were preserved at certain intervals of time 

 and the transplanted eyes were cut in sections. Eyes preserved 

 at equal intervals of time were then compared with each other. 

 It was found that the transplanted eyes of the same series which 

 had lived on the host for the same period of time may show 

 considerable differences in the rapidity with which they under- 

 go regeneration, even if they are subjected to equal conditions 



