Regeneration in Compound Eyes of Crustacea i8i 



brane. Although the retinulae are the first to collapse their 

 remains are the last to be gotten rid of. Evidently the pigment is 

 absorbed and removed only with difficulty. Often in regenerating 

 eves that have completely regenerated new ommatidia much of the 

 old pigment remains. 



The cell bodies of the retinulae after losing their pigmented 

 processes appear as large nuclei surroimded by a narrow zone of 

 condensed cytoplasm. Within a short time these cells become 

 scattered widely through the eye. After a few days their nuclei 

 appear irregularly shaped and soon afterward become conspicu- 

 ously polymorphic (Fig. 75a and b). In the usual course of 

 events these retinular cells disintegrate and disappear. But under 

 some conditions they apparently remain and later multiply and 

 give rise to an abnormal development of tissue that secretes pig- 

 ment. 



The rhabdoms and the inner ends of the cones also degenerate 

 within a short time after the retinulae. The cones continue to dis- 

 solve from the proximal ends distally. The last parts to disappear 

 are the outer ends in which are embedded the cone nuclei. Before 

 the dissolution of the cones is complete the cone nuclei appear 

 greatly enlarged and stain deeply. Their enlarged appearance is 

 probably largely due to the disintegration of the cone substance 

 from about them. 



As the disintegration of the tissues proceeds the interior of the 

 eye becomes filled with a granular mass containing scattered 

 nuclei and masses of pigment. This granular mass which is 

 usually very much vacuolated is made up of the remains of the old 

 tissues together with more or less of coagulated plasma and blood 

 cells. Sometimes the remains of the old cones appear as long 

 tapering bands of granular material extending from the periphery 

 inward. 



Fig. 51 represents a small area of the disintegrated ommatidial 

 structures as it appeared in the eye of Palaemonetes ten days after 

 the operation. Only two or three nuclei lie close beneath the 

 cuticle and a few others lie scattered deeper in. Most if not all of 

 these more deeply located nuclei are the remains of the old omma- 

 tidial structures. In the lower part of the figure are some old 



