Sorensen, Study of Epiphysis and Roof of DienccpJialon. 19 



The last changes consist in the contraction of the cavity of the 

 recessus infrapinealis, by which a slender stalk is formed. The 

 stalk arises by the approximation of the walls of the recessus, 

 and consists in front, of the vertically upheaved part of the tela 

 choroidea media and posteriorly of a narrow lamella, which 

 projects from the post cerebral commissure to the pineal gland. 

 The gland of adult birds. The hemispheres of the cere- 

 brum, and the cerebellum in birds are originally widely sepa- 

 rated from one another and over the roof of the diencephalon 

 and mesencephalon there is an abundance of connective tissue 

 in which lies the pineal gland. But during their development 

 the cerebrum and cerebellum would touch were it not for the 

 connective tissue between them. At the same time the gland 

 retains a kind of capsule from the surrounding pial-tissue. In 

 fully developed birds the gland lies in a three cornered cavity 

 between the anterior surface of the cerebellum and the posterior 

 limit of the cerebral hemispheres. Its distal thick end extends 

 to the dura mater and is joined to the latter by a stout filament. 

 The gland consists of two parts, the gland body, and the stalk. 

 From the development we have arrived at the necessary conclu- 

 sions concerning the signification of each. In the stalk we find 

 a continuation of the ventricle cavity, a remnant of the wide em- 

 bryonic recessus infrapinealis which, through the approach of 

 the cerebrum and cerebellum is pressed together. Anteriorly 

 the stalk consists of a vascular plexus-like formation, arising 

 from the epithelium of the roof of the ventricle, posteriorly of 

 a nervous lamella proceeding from the post cerebral commissure 

 and gradually thinning out. In the glandular bodies we find 

 large and small roundish vesicles, also short funnels with a cav- 

 ity filled with a liquid. The walls of the hollow bodies consist of 

 high narrow cylindrical cells, then on the outside, round cells in 

 several layers, between which the projections of the cylindrical 

 cells can be traced, and finally the whole is surrounded by a 

 thick connective tissue which forms a sort of capsule. The 

 above described structures are best recognized in the turkey 

 cock (Meleagris gallopara) where the entire gland is 5 mm. long, 

 2.5 mm. thick and the follicle has a size of .08-. 20 mm. with a 



