Regeneration in Conipound Eyes of Crustacea 239 



b The new cuticle is secreted before a continuous hypodermis 

 has formed over the wound. It is continuous with the inner 

 layers of the cuticle over the eye stump. 



3 New hypodermal cells over the ommatidial region may arise 

 in two ways; either by the transformation in situ of corneal hypo- 

 dermal cells into less specialized, actively multiplying hypodermal 

 cells, or by the proliferation of new hypodermal cells inw^ard from 

 the edges of the cut. 



4 Any injury to the eye is always accompanied by extensive 

 degeneration of the remaining tissues. Sometimes the entire eye 

 suffers destruction. 



5 The rate of regeneration is considerably affected by the rate 

 of disintegration and the removal of injured parts. 



6 Active regeneration may be in progress at the periphery 

 while deeper below the surface the injured structures are not yet 

 removed. 



7 In the regeneration of an eye all of the new structures arise 

 from the hypodermis. 



8 Multiplication of cells takes places by amitotic divisions. 



9 The cells for the retinulae are the first to differentiate from 

 the hypodermis. Their differentiation may begin before a con- 

 tinuous hypodermis has developed. 



10 The retinular nuclei move inward from the periphery, 

 elongate and divide along their radial axes, and extend proximal 

 processes through the basement membranes to the optic ganglion. 

 Thereby nervous connections are established in the regenerating 

 region. 



11 Not until after the retinular processes have extended into 

 the optic ganglion is the differentiation of cones established. The 

 cones differentiate from the periphery inward. 



12 The rhabdom is developed from the inner ends of the retinu- 

 lar cells and is at first present as a slender homogeneous rod of 

 uniform diameter, which extends from the inner end of the cones 

 to the basement membrane. The spindle shaped enlargement of 

 the rhabdom does not appear until after all the other parts of the 

 ommatidmm have been differentiated. 



13 The hypodermis does not become a true corneal hypodermis 



