217] REGENERATION OF CRAYFISH APPENDAGES 29 



regenerating corneal facets. A crayfish, from which a part of 

 the eye had been removed, moulted, and a week or ten days later 

 died. The tissues were of course in such a condition that they 

 could not be used for histological purposes, but the cuticular 

 portion was stripped ofif and examined and the softer tissues 

 beneath teased out and examined under a microscope. The in- 

 ner tissues showed no sign of either ommatidia or pigment, but 

 a part of the cuticular covering appeared to be developing irreg- 

 ular corneal facets. To be sure, without more evidence than this 

 it is impossible to say whether or not the eye is really regener- 

 ated. A single instance in which the parts removed are wholly 

 restored is sufficient to prove that functional regeneration may 

 take place, but as yet this single instance is lacking. 



However, at the present writing. May 3, 1901, a small cray- 

 fish from which a part of the cornea had been removed on April 

 9, moulted. Externally, the regenerated eye presents a more 

 normal form than any I have as yet seen, but no corneal facets 

 are visible and the eye is not as dark in color as normally. It 

 has been fixed in Flemming's fluid preparatory to sectioning. 

 Judging from the exterior, this is the most favorable material 

 of the sort that I have had. Fig. 26, PI. IV, shows an external 

 view of the eye. The part of the cornea removed was taken 

 somewhat to one side rather than at the distal end. This is still 

 evident in the regenerated eye from the apparent encroachment 

 of the stalk portion upon the corneal portion shown at c. Oth- 

 erwise, the eye has much the same appearance as the normal one, 

 except that the corneal portion is relatively much smaller. 



Since writing the above the eye shown in Fig. 26 has been 

 sectioned and another crayfish in which the entire cornea had 

 been removed has moulted (Fig. 35, PI. IV). Both eyes of the 

 latter have been sectioned. Sections of the eye, shown in Fig. 26, 

 PI. IV, disclose several interesting features. On one side and 



