Regeneration in Compound Eyes of Crustacea 197 



dating at the lower end into the rhabdom in most cases. But in 

 Vespa he describes the inward prolongation of the cone cells as 

 enclosing the rhabdom. Parker ('00) describes the prolongation 

 of the cone cells in Homarus as extending to the basement mem- 

 brane and inclosing the rhabdom in the same manner. The 

 description of the relation of the rhabdom to the cone in Crangon, 

 given by Kingsley, and applied to Crustacea in general by Patten, 

 does not agree with the facts presented by the regenerating eyes of 

 Crangon, Palaemonetes and hermit crabs. Obviously, however, 

 this interpretation is in accord with that of Phillips in the case of 

 the honey bee and that of Grenacher ('74), both of whom find 

 that the rhabdom is developed as a secretion of the retinulae, and 

 do not find the cone cells extending as slender processes beyond 

 the distal end of the rhabdom. 



Concerning the source and manner of the innervation of the 

 ommatidia the results obtained in this study of the regenerated 

 eye agree only with those observers who, like Parker ('91) and 

 Phillips ('05), regard the retinular cells as hypodermal sense cells 

 which send nerve fibers into the ganglion below. It is true that no 

 special nerve methods were used in this work upon the regenerating 

 eye. But in some specimens at least the prolongation of the retinu- 

 lar processes into fibers which penetrate the optic ganglion is clearly 

 evident (Fig. 62). In many other cases the processes can be 

 traced from the retinular nuclei to the basement membrane and 

 similar processes are found branching among the ganglion cells 

 below it. But in no case is there the slightest evidence that the 

 ganglion cells are sending fibers upward to the regenerating 

 ommatidia. Consequently there seems to be no room for reason- 

 able doubt that the retinulae form the nerve endings of the omma- 

 tidia. 



In this particular these results differ from those of Patten, 

 Kingsley and other workers on the embryological development of 

 the eye of certain Decapods. These investigators regard the nerve 

 connections as being formed by the extension of processes upward 

 from the ganglion cells, through the rhabdom and into the cone. 



The observations made in this work seem neither to uphold nor 

 to oppose the views of those who find that the ganglion cells send 



