PARAPHYSIS AND PINEAL REGION IN REPTILIA 367 



cephalic being the future eye, the more caudal the future epiphy- 

 sis. Francotte suggested the following explanation, namely that 

 the first vesicle to appear was the eye and the second coming 

 behind it was the epiphysis. This latter outgrowth developed 

 so close behind the former that it appeared almost to spring from 

 its posterior wall, and as the two grew larger they became com- 

 bined into what was apparently one vesicle. He shows (30), fig. 

 A, two outgrowths, one immediately in front of the other. In 

 figs. 7, 8 and 9 he shows a large one and then a smaller one close 

 behind the base of the larger. I am inclined to agree with this 

 explanation of Francotte. Fig. 6 shows a large cephalic vesicle, 

 then comes a very narrow lip and then a smaller caudal vesicle 

 directed somewhat backward from the former. The first is the 

 eye, the second the epiphysis. They have a common opening 

 into the diencephalonfrom which the cavities of each slant caudad 

 and cephalad. The lip between the two, which looks like a sort 

 of septum partly dividing a single vesicle, is really the line of 

 division between the two primary outgrowths which arose indi- 

 vidually from the roof of the diencephalon. Therefore, the single 

 outgrowth E seen in fig. 5 would be realty the pineal eye and the 

 smaller caudal outgrowth in fig. 6 has probably appeared second- 

 arily and will form the epiphysis. This latter, therefore, corre- 

 sponds to the single evagination in the turtle, £',fig. 18, where there 

 is no pineal eye. This view of the individuality of the pineal eye 

 is I believe now generally accepted although certain writers still 

 claim that it is a differentiation of the distal end of the epiphysis. 

 Another matter of interest is the question of the bilateral origin 

 of the pineal outgrowths. According to the results of Beraneck, 

 Dendy, Hill, Locy and Cameron it seems that there are in very 

 early stages two bilateral outgrowths, one of which is always 

 smaller than the other and soon disappears. Cameron (14, 16) 

 shows these clearly in the chick and in amphibia and Dendy in 

 Sphenodon. Both these writers found that the left outgrowth 

 always persisted. Locy in elasmobranchs and Hill in teleosts 

 and Amia also observed bilateral evaginations. In Amia Hill 

 found that the left one disappeared while the right one devel- 

 oped. Cameron argues that the fact that the nerve to the pineal 



