Sorensen, Study of Epiphysis mid Roof of Diencephalon. 25 



the cavity of the pineal and the ventricle in earlier stages of de- 

 velopment and also apparently in the adult brain of the salmon. 

 In Cyprinoides (Leuciscus) the glandula pinealis appears as a 

 flat cake which lies far in front on the Frontal, while the tubular 

 stalk is enveloped by the plexiform boundary formed by the 

 pia mater. 



In (7^-86) Rabl-Ruckhard calls attention to the fact that 

 in his articles (72- 82) and (72-84) he had arrived at the same 

 conclusions that de Graaf presented in '86. In his article which 

 appeared in 1884 he says: The skull-roof of the large fossil 

 Enaliosaurians of the Lias, of the Icthyosaurians and of the Ple- 

 siosaurians, has an unpaired foramen which corresponds to the 

 foramen in the parietal-bone of Sauriens. Perhaps here also lay 

 the distal end of the highly developed pineal organ, and we 

 could easily suppose its function to be not so much that of a 

 visual organ, as a temperature sense-organ intended to warn its 

 possessor of the intense effect of the tropical sunbeams, when 

 it lay at rest on the shore and sandbanks like the present croco- 

 diles. He says further that Leydig had expressed similar views 

 in '72 and '81. 



Huxley (38-76, p. 29) writes: Dorsally the thalamen- 

 cephalon is continued upwards and forwards into the subcylin- 

 drical peduncle of the pineal gland. This is a large heart-shaped 

 body, whose base is turned downwards and backwards. The 

 apex is connected by fibrous and vascular tissue, with a depres- 

 sion in the cartilaginous roof of the skull. 



Beauregard 1 (5a- 81, No. 16, p. 233) says that the supe- 

 rior part of the diencephalon is composed of a little lamina 

 slightly curved toward the anterior concavity separated from the 

 posterior face of the hemispheres by a deep transverse cleft. 

 The aperture of this cleft is closed by a transparent membrane 

 in which is enclosed a little cordiform mass of opaque matter 

 which appears to correspond to the epiphysis and is supported 

 upon the posterior commissure of the two hemispheres. 



Wiedersheim (p5-'86, p. 181) says: Dorsally the dien- 



^ide Burkhardt. 



