DEGENERATE EYES IN THE CUBAN CAVE SHRIMP. 2/5 



Several questions arise to which no satisfactory answer can at 

 present be given, (i) To what extent has the internal morphol- 

 ogy of the neurones of the adult optic ganglion been modified by 

 degeneration ? (2) To what extent has the degeneration of the 

 axones affected the cephalic ganglion of the animal ? (3) What 

 is the condition of the eyes in the embryo? The neurones of the 



ct 



It 



n 





-d 



- ml 



-h 

 i 



FIG. 7. Same eye as in r'ig. 6, but different focus, x 1,000. n, a nerve fiber 

 ending in r/, a retinula cell; tf, coagulated hremolymph ; >/il>, bounding membrane 

 of optic nerve ; b, fiber of optic nerve ; h, hypodennis ; ft, corneal cuticula. 



Microphotographs by Dr. D. W. Dennis, Earl ham College, Richmond, Indiana. 



optic ganglion seem to have degenerated so much that their 

 internal morphology is enigmatical. No nuclear wall nor chro- 

 matin threads could be seen in any of them, even when stained 

 with iron haematoxylin. It is an open question what the phy- 

 logeny of the decapod eye has been, and what bearing the pres- 

 ent case of degeneration may have on the Law of Biogenesis. 

 The embryological history might throw some light on this latter 

 phase of the question, but it has been impossible so far to find 

 embryos. 



