213] REGENERATION OF CRAYFISH APPENDAGES 25 



an internal examination of the regenerated eyes of individuals 

 that had died. In every case I have kept a record of the time 

 occupied by the experiment and of the season of the year. With 

 these preliminary statements, which apply equally to both cases, 

 I shall proceed to the discussion of observations and results. 



(a) Regeneration After Removal of a Portion of the Eye. 

 Under this heading are included the cases in which a part 

 of the cornea and those in which the entire cornea has been re- 

 moved. Removal of the whole or a portion of the cornea is al- 

 ways attended with more or less bleeding, but a clot of blood is 

 soon formed. Within half an hour after the operation the inner 

 tissues bulge out above the level of the cut edges. The swollen 

 appearance persists for a few days, and in the meantime a brown- 

 ish crust is formed over the cut surface. This gives the appear- 

 ance of a very rapid regeneration, while in fact practically none 

 has taken place. Later the swollen end seems to retract, and ex- 

 ternally regeneration does not appear as advanced as before. 

 The swelling and subsequent contraction may give rise to the 

 extremely irregular contour which a regenerated eye usually 

 presents. From now on an actual growth takes place and within 

 a few weeks or months, as the case may be, the eye attains a size 

 approximately equal to that of the uninjured one. One specimen 

 in which the top of the eye had been removed on October 29 had 

 apparently undergone a very considerable regeneration by No- 

 vember 10 ; by the eighteenth of November the eye had regained 

 almost its full size. A casual observation showed no particular 

 difference between this eye and the normal one, except in color. 

 The regenerating eye was brown instead of nearly black, the 

 color of the uninjured eye. Examination of the new growth 

 with a lens, however, showed immediately that no corneal facets 

 had been formed, and, since neither corneal facets nor retinular 

 pigment had been developed, it can not be said that there was 



