Regeneration in Compound Eyes of Crustacea 179 



cut, which later multiply until a complete hypodermis is formed. 

 In either case the first new nuclei must be contributed by the 

 remaining hypodermal cells. Whenever the cut has not removed 

 the entire ommatidial portion the remaining corneal hypodermal 

 cells must assume a somewhat less specialized role in order to 

 form the first new nuclei of the regenerated hypodermis. 



B REMOVAL OF THE INJURED TISSUE 



The fact that the inner tissues of the eye are so much softer than 

 the chitinous outer covering renders it impossible to operate upon 

 the eye in any way or to remove any part of it without serious 

 injury to the remaining softer tissues. It is evident that, before 

 any considerable regeneration can take place, the injured tissues 

 must be either repaired or removed. All the observations made 

 upon regenerating eyes tends to show that none of the injured 

 tissues except the hypodermis ever repair themselves. 



Sections of an eye fixed six and one-half hours after the operation 

 show that considerable changes have already taken place in the 

 injured tissues. The effect is particularly noticeable in the 

 retinulae. Many of the retinular nuclei have become separated 

 from the pigmented retinular processes and appear as rounded 

 bodies surrounded by a 'dense mass of cytoplasm. These are 

 irregularly scattered among the other tissues. Some parts of the 

 interior have become fairly clear of the broken down structures 

 and are occupied chiefly by coagulated plasma. In other parts 

 of the eye the injured tissues lie in confused masses. 



The changes in the next twelve or fifteen hours do not show 

 much advance over the earlier stages. The interior still presents 

 a badly confused mass of broken down tissue. In some parts, 

 however, the cone nuclei appear larger, the bodies of the cones 

 have begun to dissolve and the number of rounded retinular cells 

 appear somewhat more numerous than in the earlier stages, their 

 nuclei showing irregularities in shape (Fig. 75a and h). 



During the earliest stages, six to sixty hours after the operation, 

 the ommatidia that are still intact always appear bent and twisted 

 out of their normal positions. Later stages show that these 



