APPENDIX 
In the introduction mention was made of the extirpation of 
the lens. As, however, not many animals survived this oper- 
ation for any length of time, there was not enough material at 
my disposal to enable me to give any kind of detailed account 
of the regeneration of this organ. After extirpation of the lens 
the injured eye lost its ability to perceive light. A few animals, 
however, survived the operation and lived for over ten weeks 
after it had been performed. On these animals I noticed that 
the injured eye had regained its sensitiveness to light after a period 
of about eight weeks. This fact was ascertained in the following 
manner. It is well known that the circular pad of skin which 
surrounds the visible parts of the eye acts as a lid. If the eye 
is suddenly exposed to light, this pseudolid shuts. If I exposed 
an eye to the light whose lens had been extirpated a few days 
previously, then the pseudolid did not close. Ten weeks after 
operation, however, the same eye showed the characteristic 
contraction of the pseudolid when suddenly exposed to light. 
Some animals even survive the loss of a whole eye. While at 
Naples I one day received a sepiola (from Doctor Naef), which 
had completely lost its one eye. The wound was healed, but 
I could not detect any signs of regeneration. Perhaps the animal 
had been injured just a few days before its capture. 
