32 



i i;i:i)i:i;i( K TILXKY AND LUTHER F. WARREN 



and plexiform, in many forms attaining a marked vascularity. 

 The next structure in the pineal region is the commissura habenu- 

 laris, following which is a long pars intercalaris anterior. Then 

 fallows the epiphy-i- or the proximal portion of the pineal organ 

 with a marked pineal recess. There can be little doubt that 

 this particular form in which the pineal organ presents itself 

 i- the actual proximal part of other species. Following the 

 epiphysis is a thick pars intercalaris posterior, and finally the 

 posterior commissure. 



Po 



Npin 

 ' 



L'-V"-'- 1 i-i-Lir J ly-tri-iET i 1 1 1 1 ii vrj , TJIIII_IT, j t rjirr^ 



Fig. 4 Schematization of the pineal region in Amphibia, according to Stud- 

 nicka, 1905. 



/-v., lamina tcrminalis; Pf., paraphysis; I)*., dorsal sac: Ch.. commissura ha- 

 benularis; /'<., pineal organ; A'/*///, IHTVUS pinealis; !'/>., proximal portion pineal 

 MM.III: '/'/).. tract us pinealis; Sch., pars intercalaris posterior; Cp., commissura 

 posterior; M ., midbrain. 



7. The pineal region in rcptiia 



In IM-osaurians and Saurians, as in Petromyzon, and some 

 teleosts, both the pineal and para.pin al organs make their appear- 

 anci-. lint the order which they hold in the lower forms is some- 

 what reversed here since the parapineal organ gives rise t<> an 

 eye-like sti'ucture called the parietal eye. This parietal eye, 

 h \\e\rr. is |)i-esenl only in the lower reptiles. The pineal organ, 



