PIGMENTATION OF THE PINEAL REGION IN FISHES 73 



in the cells of the end-vesicle or the stalk of the pineal organ of fishes, 

 and it seems probable that pigment is not generally present in the end- 

 vesicle of fishes. Although from the developmental standpoint the end- 

 vesicle appears to represent the part of the primary pineal diverticulum 



L '•---- — cor 





Fig. 49. — The Pineal Organ of an Adult Spinax 

 Niger, seen in Longitudinal Section, and showing 

 the Relations of the Surrounding Structures. 



PARIETAL 

 SPOT 



which gives origin to the " pineal eye " of cylostomes, and of certain 

 Amphibia and reptiles, it evidently does not differentiate so far as to 

 represent the parietal sense-organ of these animals, and a retina with 

 sensory, ganglionic, and pigment cells is not differentiated. 



