366 JOHN WARREN 



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panded at its distal end and tapers to a rounded solid stalk at its 

 proximal end which lies between the two commissures. That of 

 the lizard is very attenuated in the adult stage. . The epiphysis 

 lies close against the caudal wall of the dorsal sack and is even 

 embedded somewhat in it, especially so in the turtle. , In most of 

 the stages the epiphysis is surrounded by vessels, figs. 11 and 20. 

 and later lies immediately beneath the superior sagittal sinus, fig. 

 22. In both the turtle and lizard the distal end of epiphysis and 

 paraphysis come almost in contact. In the latter the proximal 

 ends are separated by the wide dorsal sack and both structures 

 develop over the top of this region until their distal ends are closely 

 approximated. In the lizard the compression of the dorsal sack 

 brings not only the distal ends but also the proximal ends of the 

 two structures very close together. Francotte shows a section of 

 this region in Anguis where the tip of the epiphysis is actually 

 wrapped over the tip of the paraphysis. The epiphysis is pres- 

 ent in all forms except myxinoids, Torpedo and crocodilia, Stud- 

 nicka (90), Voeltzkow (96). 



In certain reptilia there is also present the parietal or pineal 

 eye which lies at some distance from the epiphysis in the parietal 

 foramen, fig. 13. The pineal eye or pineal organ resembles in 

 many respects the paired eyes and has a nerve which connects 

 it with one of the ganglia habenulae. The staining of my speci- 

 mens was not favorable for the study of this nerve, but is is gener- 

 ally accepted that such a nerve exists. (Francotte, Beraneck, 

 Burckhardt, de Klinckowstrom and Dendy.) Cameron (15, 16) 

 has also shown nerve fibers passing from the ganglion habenulae 

 of one side to epiphysal elements on the opposite side forming a 

 true decussation in the superior commissure. He observed these 

 fibers in teleosts, amphibia, birds and man. 



One of the most vexed questions about the development of 

 these pineal organs concerns the origin of this so-called i ye. One 

 set of writers considered that it was formed from the distal end 

 of the epiphysis from which it was simply constricted off. An- 

 other set maintained that the pineal eye arose by an independ- 

 ent outgrowth from the brain and consequently there were two 

 evaginations, one immediately in front of the other, the more 



