THE PINEAL BODY 



127 



3. A molecular layer described by Spencer 366 and Francotte 127 

 or a layer of nerve fibers described by Strahl and Martin. 383 

 The latter observers and Klinckowstroem 206 maintain that these 

 fibers are in connection with the parietal nerve. Leydig 238 and 

 Dendy 86 believed that a cleft occurred in this layer which, ac- 

 cording to Leydig, gives rise to a lymph space. 



4. An outer cellular layer of round cells somewhat deeper than 

 the second layer. 



5. A membrana limitans externa. 



Fig. 66 The pineal eye in Iguana tuberculata, according to Klinckowstroem, 

 1894. 



The most important elements in the retina are the rod cells 

 which appear to correspond to the ependymal cells of the retina 

 in the pineal organ of Petromyzon. They are long, cylindrical 

 elements in which may be differentiated an outer 4 thread-like 

 part and a more cylindrical portion. The nucleus 'occupies an 

 enlargement in the area of transition between these two por- 

 tions. The inner cylindrical parts lie close together; the outer 

 thread-like parts have broad spaces between them in which 

 are lodged neuroglia and some ganglionic cells. The peripheral 

 processes come to the surface of the retina and spread out against 



