THE PINEAL BODY 49 



to the left of the pineal organ. It was connected with the roof- 

 plate by means of a thin stalk. In the 13 mm. embryo this 

 organ has come to lie above the commissura habenularis and 

 still later it is consolidated into a mass of cells lying to the left 

 beneath the now markedly developed and ventrally flexed 

 pineal organ. Eycleshymer and Davis 113 in 1897 confirmed the 

 observation of Hill and noted that the anterior or parapineal 



44 



Fig. 16 Mesial view of brain reconstruction of 300 mm. Mustelus. X 25. 

 The unshaded area shows the cut surfaces of the reconstruction. According to 

 Tilney, 1915. 



2, chiasmatic process; 3, cerebellum; 4, chiasm; 7, epiphysis; 10, hypophyseal 

 recess; 13, infundibular process; 14, infundibular process, saccular surface; 15, 

 infundibular process, pituitary surface; 24, midbrain; 27. mammillary body (pos- 

 terior lobe) ; 32, post-chiasmatic eminence (inferior lobe) ; 33, post-chiasmatio 

 recess (recess of inferior lobe); 36, post-infundibular evagination; 39, paraphysis; 

 40, recess of the infundibular process; 41, supra-optic crest; 42, supra-optic re- 

 cess; 44, telencephalon; 47. velum transversum. 



organ possessed a lumen late in the course of development. 

 Both the anterior and posterior pineal organs in the embryonic 

 stages have nerve fibers which connect them with the habenular 

 commissure. The earlier works upon this region in ganoids were 

 done by Salensky 341 in 1881 and Balfour and Parker 11 in 1882 

 (fig. 18). 



MEMOIR NO. 9 



