1 82 Mary Isabelle Steele 



pigment remains. The granular mass occupying the greater 

 part of the figure is made up chiefly of partially dissolved cones. 

 The slender strands which can be traced through the granular 

 mass are in part at least made up of new cytoplasm. At certain 

 points the cytoplasmic strands are seen to be continuous with the 

 inner layers of the cuticle. 



Fig. 48 is taken from a section of an eye of Palaemonetes seven 

 days after the removal of part of the ommatidia. A surface view 

 from which this figure is taken is shown in Fig. i. Practically all 

 the material represented in Fig. 48 except the cuticle is made up of 

 disintegrated ommatidia. The long band extending inward 

 shows approximately the position of a former cone. The large 

 vacuolate spaces in the upper part of the figure are old nuclear 

 remains. In the process of disintegration the nuclei at first 

 enlarge and stain deeply. Later the nuclear contents disappear 

 although the nuclear membrane persists for some time longer, 

 often becoming shrunken and folded into a variety of shapes. 



It has been seen that the disintegration of the injured tissues 

 begins immediately after the operation and that the greater part is 

 accomplished in from one to three days. The distal ends of the 

 cones alone remain intact for a much longer time, in some cases 

 from two to three weeks and occasionally even longer. The 

 removal of these disintegrated tissues is much slower than their 

 dissolution. 



Regeneration proper may and usually does begin within a few 

 days after the old structures have broken down and progresses 

 simultaneously with their removal (Figs. 49,50). One part of the 

 eye may show ommatidia differentiating while another region is 

 still occupied by disintegrated old structures. The individual 

 differences in the rate of regeneration of such frequent occurrence 

 is probably largely dependent upon the variations in the length of 

 time required for the removal of the old structures. This prob- 

 ably also accounts for the fact that regeneration does not take place 

 uniformly throughout the same eye. The part of the eye that gets 

 rid of the injured tissue soonest regenerates first. 



The above observations apply in general to all the forms used. 

 Crangon, however, offers a significant exception in that the injured 



