258 THE PINEAL ORGAN 



and they are irregularly disposed. There is a tendency towards degenera- 

 tion seen in some of the older specimens, this being evidenced by the 

 appearance of spaces between the cells and disappearance of the cell 

 outlines. Leydig and others have described the presence of granules 

 in the cells, producing an appearance of longitudinal striation. Leydig 

 also described a radially striated layer on the surface of the lens in one 

 specimen of Anguis fragilis, which somewhat resembled the layer of 

 cuticular rods seen in some invertebrate eyes. The nature of these is 

 obscure and the case seems to have been quite exceptional. On the other 

 hand protoplasmic cilium-like processes on the inner surface of the lens, 

 and projecting into the cavity of the vesicle are more common. In some 

 cases these are continuous with syncytial strands of the vitreous tissue 

 filling the cavity of the vesicle. 



C. The Vitreous Body 



In well-fixed preparations there is present in the cavity of the parietal 

 organ a delicate syncytium which consists of an irregular network of fine 

 protoplasmic strands showing a few oval nuclei imbedded in the thickened 

 nodes of the reticulum. Peripherally it is continuous with the rod- 

 or club-shaped processes of the inner layer of sensory and pigmented 

 cells of the retina and sometimes with similar tapering protoplasmic pro- 

 cesses which project inwards from the inner surface of the lens. In 

 one case a thickened band of protoplasm containing closely packed 

 nuclei extended inwards from the retina with which it appeared to be 

 continuous. It is probable that during life the meshes of the reticulum 

 contain a clear albuminous fluid. In imperfectly preserved specimens 

 this tissue may be condensed and form an almost uniform layer lining 

 the inner surface of the retina, and appearing as a coagulum. In other 

 cases it may be thrown down as a flocculent precipitate which occupies 

 the whole cavity. The few cases in which a true syncytium has been 

 demonstrated indicate that in the living animal there is normally a definite 

 syncytium, enclosing spaces filled with clear fluid, and similar to that 

 described in the median eyes of Petromyzon and Geotria and in the lateral 

 eyes of vertebrates generally. 



Nerve Supply of the Pineal System of Sphenodon 



The nervous system of adult specimens of Sphenodon was minutely 

 studied by Dendy in 191 1, who employed serial transverse and longitudinal 

 sections stained with picro-indigo-carmine. He described (1) a left 

 pineal nerve (n. parietalis) and (2) a right pineal nerve (tractus pinealis). 



