PARAPHYSIS AND PINEAL REGION IN REPTILIA 317 



Fig. 6 shows the brain of Lacerta muralis of 3.2 mm. In the 

 paraphysal arch three small evaginations, P, have made their 

 appearance, which represent the anlagen of the paraphysis. 

 The velum is seen at the sharp angle immediately behind the 

 third evagination, and extending backward from that point is 

 the post velar arch, forming a well marked curve in the dience- 

 phalic roof. There are now two pineal evaginations with a sort 

 of common opening into the diencephalon. The larger or ce- 

 phalic outgrowth corresponds to that seen in fig. 5 and is the anlage 

 of the future pineal eye, P. E. This will break away from the 

 other vesicle and migrate eventually to the parietal foramen. 

 The smaller or caudal outgrowth is really secondary and has de- 

 veloped immediately behind the former. This will be the future 

 epiphysis, E., and will always be attached to the roof of the dien- 

 cephalon. We have here, I think, without doubt two distinct 

 vesicles, but they lie so close together that as they develop and 

 enlarge the wall between them is pushed dorsally so that we have 

 a common opening for the two into the diencephalon. Behind 

 the epiphysis in this specimen the intercalated arch has been 

 flattened out and is not well marked. 



Fig. 7 shows the brain of Lacerta agilis of 3.6 mm. In this 

 case there is only one paraphysal outgrowth and there is probably 

 a considerable variation in the number of the primary paraphysal 

 outgrowths in different forms and stages of lacerta. The velum 

 appears as a sharp angle in the roof and is continued laterally into 

 a well marked ridge projecting into the brain cavity. Anterior 

 to this ridge the hemisphere is now very well developed, with the 

 deep opening of the optic stalk just inferior to it. The post velar 

 arch is essentially the same as in the preceding figure. The two 

 outgrowths, the future pineal eye and the epiphysis, are seen 

 from the outside and of the two the cephalic is much larger than 

 the caudal. Their internal arrangement and opening into the 

 diencephalon is practically the same as in fig. 6, the separation 

 between the two vesicles being more marked, however. 



Fig. 8 shows the brain of Lacerta muralis of 4.5 mm. Here 

 again there are three well marked primary paraphysal outgrowths 

 in essentially the saniQ position as in fig. 6. The velum appears 



