Regeneration in Compound Eyes of Crustacea 221 



The appendage shown in Fig. 28 developed in twenty-four days 

 with the intervention of one moult. It is of interest because of the 

 indications that the optic nerve has extended through almost the 

 entire length of the regenerated appendage. It is also of interest 

 because of the ganglionic swelling that appears to be associated 

 with the nerve in its distal half. 



Fig. 41 shows an unique type in that the appendage is curved 

 closely back until the free end almost touches the head. Although 

 this appendage is made up of several segments it was rigid from 

 its first appearance. 



The remaining examples of these appendages are of approxi- 

 mately the same character as those figured. They belong chiefly 

 to the type shown in Fig. 34, except that two of them show a 

 larger number of tubular hairs. One of these belongs to a speci- 

 men that moulted twice and was not killed for sixty-seven days 

 after the operation. The regenerated appendage shows but little 

 advance over those that were fixed at the end of half that time. 

 It is still no longer than the normal eye stalk and shows no greater 

 number of sensory hairs than are seen in Fig. 30. The additional 

 facts obtained from an examination of the sections will be referred 

 to at the close of this section in the general discussion of their 

 significance. 



2 Cases that Show No Especial Regeneratioji 



As was stated above out of the thirty-six crabs that moulted one 

 or more times only ten developed heteromorphic appendages 

 while twenty-six showed no- particular regeneration. The propor- 

 tion is a little more than 30 per cent to a little less than 70 per cent 

 in favor of those that showed merely a healed over stump. 



The stumps that show no actual regeneration present a variety 

 of shapes and characters. None of them, however, show any 

 signs of pathological pigment development. From all appear- 

 ances the failure to regenerate in most instances was due to a lack 

 of sufficient regenerative activity to produce the new tissue neces- 

 sary. In some cases where the eye was taken off even with the 

 head the wound healed over leaving a smooth surface, not so much 

 as a slight elevation marking the former position of the eye. In 



