Regeneration in Compound Eyes of Crustacea 165 



The experimental part of the work was begun at the University 

 of Pennsylvania. Observations upon Hving material were also 

 carried on during two summers at Woods Hole, Mass., and one 

 summer at Cold Spring Harbor, L. I. The greater part of the 

 detail work of examining the preserved material has been done at 

 the University of Missouri during the present year. 



In closing I wish to express my thanks to Dr. E. F. Phillips and 

 Dr. D. B. Casteel for the care of experiments; to Dr. E. G. Conklin, 

 University of Pennsylvania; Dr. C. B. Davenport, Carnegie 

 Institute at Cold Spring Harbor, and Dr. George Lefevre and 

 Dr. W. G. Curtis, of the University of Missouri, for their interest 

 and valuable suggestions during the course of the work. 



II Material and Methods 



The small hermit crab, Eupagurus longicarpus, the common 

 shrimp, Palaemonetes vulgaris, and the sand shrimp, Crangon 

 vulgaris, afford the greater part of the material used in the series 

 of experiments to be described in this paper. For comparison 

 two species of crayfish, Cambarus virilis and C. gracilis, a species 

 of fresh water Ascellus, the common (wood-louse), Oniscus, and 

 the fresh water Gammarus were used. Other Crustacea also 

 were experimented upon but since no decisive results were obtained 

 they need not be considered here. 



The work has been confined chiefly to the eyes of the forms 

 used although experiments upon the appendages, particularly the 

 antennae, were conducted at the same time. These were, however, 

 largely for the purpose of comparing relative rates of regeneration 

 of the different parts, especially the rate of regeneration of the 

 appendages as compared with that of the eyes. 



The experiments upon the eyes consisted in either the removal 

 of a part of the eye or of the whole eye. The part removed varied 

 greatly in the different series of experiments and more or less in 

 individuals of the same series. A limited number of experiments 

 upon Palaemonetes included the removal of both eyes or the 

 removal of one eye with a part of the brain; these operations in 

 most cases resulted fatally. The effect of splitting the eye was 



