Regeneration in Compound Eyes of Crustacea 185 



these respects the regenerating eyes investigated in this series of 

 experiments offer a uniqiTe instance in their method of cell division. 



V Regeneration Occurring after Destruction of 

 Distal Part of Eye 



Under this heading will be discussed the results obtained from 

 eyes injured in varying degrees but not exceeding the destruction 

 of more than the distal two sections of the optic ganglion. The 

 injury originally inflicted varied from tearing the surface of the 

 cornea with a needle to cutting off the whole top of the eye so that 

 at least the first part of the second section of the optic ganglion had 

 been removed. Frequently, however, as has been explained in 

 Section IV the part of the eye ultimately lost was much greater than 

 that originally removed. For in cutting the eye with scissors or 

 tearing it with a needle much of the tissue surrounding and under- 

 lying the wound was so injured that it afterward degenerated. 



In the series of experiments to be described under this division 

 nearly two hundred Palaemonetes, twenty Crangon and fifty 

 hermit crabs were used. Fifty per cent of the Palaemonetes, 5 per 

 cent of the Crangon and 10 per cent of the hermit crabs died of the 

 operation. Of those that survived the loss of blood and the 

 nervous shock of the operation a considerable number died from 

 other causes without having undergone a moult. Forty-five 

 Palaemonetes, seventeen Crangon and twenty-nine hermit crabs, 

 however, lived through at least one moult. Among these a num- 

 ber showed no regeneration either from surface examinations or 

 from sections. The greater number of those that gave surface 

 indications of regeneration and for comparison a number that 

 showed no regeneration have been sectioned and examined. 



A regeneration of the functional eye 



Experience has shown that the number of days an experiment 

 covered serves to indicate only in the most general way the stage 

 of regeneration. While the time element naturally constitutes a 

 most important factor the rate of regeneration is also dependent 

 upon the season of the year, the age and the physiological activity 



