Regeneration in Compound Eyes of Crustacea 189 



removed. The regenerated eye shown in the figure was developed 

 within thirty-three days and after only one moult. This moult 

 occurred on the thirty-second day and the eye was fixed in Perenyi 

 the thirtv-third day. Sections show that ommatidial structures 

 have been fully differentiated although incompletely developed. 

 One point is particularly noticeable in these sections; the omma- 

 tidia are very much shorter than in the normal eye. This condition 

 was probably caused by the mechanical pressure of the covering 

 cuticle which forced the developing ommatidia into less space than 

 they would otherwise have occupied. Fig. 13 shows the eye of a 

 hermit crab regenerated from a stump in which not more than half 

 of the optic ganglion remains. The regeneration in this eye took 

 place in thirty-eight days. One moult occurred twelve days after 

 the operation. Although extremely small the eye is practically 

 perfect except that the corneal facets have not yet developed. 



Figs. 14 and 15 show two other regenerated eyes of hermit crabs 

 forty-one and sixty-seven days respectively after the operation. 

 Sections of the forty-one day eye do not show ommatidia as fully 

 developed as the thirty-eight day specimen previously described. 

 The sixty-seven day specimen shows the eye complete in all its 

 details even to the corneal facets. Whether a younger regenerated 

 eye might not show the corneal facets has not been determined 

 since no specimens were available between the forty-one day and 

 the sixty-seven day specimens. 



A noticeable feature in all the regenerated eyes of the hermit 

 crabs is their small size in comparison with the normal eyes. It is 

 probable that the regenerated eyes would have increased in size 

 if the experiment had covered a longer period of time. Sections of 

 the eye shown in Fig. 12 indicate that the definitive size has not 

 been reached. For, lying outside the fully formed ommatidia are 

 others in the process of development. In the case of the eye 

 shown in Fig. 13 sections do not show any indications of partially 

 developed ommatidia and it may be that this eye would never have 

 reached the size of the normal eve. Perhaps this is what we should 

 expect since the amount of nervous tissue present is considerable 

 less than is normal. 



It is more difficult to mterpret the actual condition of a regener- 



