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FREDERICK TILNEY AND LUTHER F. WARREN 



marked tractus pinealis, nevertheless in a certain number of 

 instances a nerve tract may be observed connecting the pineal 

 organ with the roof of the interbrain. 



In Ophidia the pineal organ is rudimentary. Only the prox- 

 imal portion persists in the snakes. This, however, has under- 

 gone considerable modification from the proximal portion already 

 encountered in the lower vertebrates. In the true snakes it is 

 a compact, highly vascular structure to which the term epiphysis 

 or corpus pineale may, in the strict sense, be applied. Hoff- 



Epid 



Pa 



Fig. 63 The epiphyseal complex in Anguis fragilis, according to Leydig, 

 1891. 



P. a., parapineal organ; Ep., proximal portion of pineal organ. 



mann 186 in 1886 showed that the corpus pineale in ophidia begins 

 in its development as a simple evagination from the interbrain 

 roof. How it attains its later complicated, compact form is not 

 yet exactly known. No doubt the solid epiphysis due to the 

 proliferation of the wall of the anlage causes the obliteration of 

 the lumen of the original evagination. A paraphysis develops 

 early in ophidians and has in its inception the same general form 

 as the epiphysis. The pineal region in the adult consists, there- 

 fore, of a paraphysis which is a thick-walled structure associated 

 with the chorioid plexus, a velum transversum and a dorsal sac 



