84 



FREDERICK TILNEY AND LUTHER F. WARREN 



of the pineal organ the pellucida. Histologically the pellucida 

 is, according to Ahlborn 2 made up of cells of considerable size 

 together with connective tissue. Owsiannikow 296 found both 

 fibers and small cells. Whitwell 421 and Beard 18 in 1888 found 



Fig. 47 Retina and pellucida of the pineal organ in a full-grown Petromyzon 

 marinus, according to Studnicka, 1899. 

 Pell., pellucida; Ret., retina. 



that the pellucida consisted of cylindrical cells. Gaskell 145 in 

 1890 observed cylindrical and small cells, and Studnicka 388 as 

 well as Retzius 3318 found that the structure was made up almost 

 exclusively of large cylindrical cells. 



