Regeneration in Compound Eyes of Crustacea 227 



regardless of the time of the experiment and the size of the stump, 

 are similar to the one shown in Fig. 33, No. 13 in the table. Fig. 33 

 shows the nerve stump flush against the healed end. The indica- 

 tions from sections and surface views are not such as to lead one to 

 expect that further regeneration would have ever taken place. 

 Fig. 26 represents the only stump that even suggests the develop- 

 ment of a heteromorphic structure. As the table shows this 

 specimen lived only twenty-four days, during which time it 

 moulted twice, and regenerated the tiny mass of new tissue repre- 

 sented by the darkly stippled portion of the figure. The eye was 

 completely removed, the cut coming at the level of the attachment 

 of the eye to the head, represented in Fig. 26 by the line a-b. Fig. 

 27 represents a more highly magnified view of the stump. 



The remaining figures in the series, Fig. 35^, b, c, show the 

 maximum regeneration, yet in none of these cases did the experi- 

 ment cover more than thirty days. Apparently regeneration in 

 most cases proceeds to the forming of the hypodermis and cuticle, 

 which may be extended slightly beyond the nerve trunk by loose 

 strands of connective tissue, and then stops. Fig. 35^^ shows more 

 than the usual amount of new tissue. The line a-b represents 

 the level of the union of the eye with the head. The unshaded 

 central part of the eye stump shows the remains of the optic nerve; 

 the shaded peripheral portion shows the new tissue. Neither 

 sections nor surface examinations give the slightest evidence of the 

 regeneration of nerve fibers, or of any special diff^erentiation of the 

 regenerated tissue. 



D THE HISTOLOGY OF THE HETEROMORPHIC APPENDAGES 



The microscopic structure of the antenna-like appendages has 

 not been considered in great detail because suitable material has 

 been wanting. In the whole series of experiments only ten hermit 

 crabs and one Crangon ever regenerated a heteromorphic append- 

 age in place of the excised eye. Several of these died and were 

 preserved in alcohol. From such material no detailed results were 

 obtainable. Again, the only sections of any particular interest 

 and value are longitudinal ones. These heteromorphic append- 



