THE PINEAL SYSTEM OF AMPHIBIA 



233 



parietal) bones, close behind the ethmoid and thus just above the olfactory 

 lobe. Having entered the cranial cavity, it courses backwards on the 

 superficial aspect of the dura mater, to which it is closely applied, to the 

 paraphysis. It then passes over the latter to the epiphysis. In its 

 course thither the nerve is pushed for a short distance away from the 

 median line by a dense plexus of blood-vessels. Braem saw the commence- 

 ment of the nerve near the apex of the epiphysis, but he was unable 

 to see any connection of its fibres with those of the " tractus pinealis," 

 although he considered such a connection was more than probable. 

 Studnicka also mentions that he was unable to trace any connection between 

 the pineal nerve and pineal tract in his specimens of quite young tadpoles 

 of Rana. Braem saw no indications of degeneration ; nevertheless, he 

 considered it possible that the nerve in some cases might be absent, an 

 opinion which is supported by the observations of de Graaf and Leydig, 

 and by a young specimen of a frog tadpole, of our own (Fig. 167). 



The course of the pineal tract in an adult specimen of Rana temporaria 

 Epd. 



Fig. 167. — Section through Stieda's Organ of a Frog Tadpole, at a Later 

 Stage of Development than that shown in Fig. 164. 



The terminal vesicle (parietal organ) is completely cut off from the epiphysis, 

 and careful search through sections behind the vesicle failed to reveal any 

 nerve tract or remnant of the original connection between it and the epiphysis, 

 or brain. (Original, R. J. G.) 



Cr. C. : cranial capsule ; Epd. : epidermis ; St. O. : Parietal organ (Stieda). 



