THE PINEAL BODY 121 



Platydactylus. In some cases, as in Gehyra oceanica and 

 Hemidaclylus mabouia, described by Stemmler 374 in 1900, the 

 entire epiphyseal complex may be only recognized in the slightest 

 rudiment possible. In one instance reported by Studnicka, 386 

 namely, Pseudopus pallasi, there is an end-vesicle, a stalk, and 

 a proximal portion. The stalk is, in fact, a double one, or, in 

 other words, there is a main stalk and a secondary accessory 

 connection between the end-vesicle and the roof-plate of the 

 brain. 



The proximal portion of the pineal organ, known as the epi- 

 physis or corpus pineale, is present in all forms. In some cases 

 the proximal portion is a simple pyriform structure attached by 

 a thin stalk to the roof of the interbrain. In other instances it 

 is spindle-shaped or oval. The walls of the proximal portion 

 are thick and usually flat inside as well as outside. In some 

 cases there are inner reduplications, as in the fish. Leydig 238 

 in 1891 found thick accessory spaces in the organ of Lactera 

 ocellaia and Anguis fragilis due to septal formation. The wall 

 may be much folded, giving the appearance of a complicated 

 glandular structure. Edinger 105 in 1890 showed this in one of 

 his cuts (fig. 63). 



The histological structure of the pineal organ. The chief cellular 

 constituent of the pineal organ, both in its end-vesicle when 

 present and in the proximal portion, is the ependymal cell. 

 Neuroglia cells also occur interspersed among the ependymal 

 elements, but there are no ganglionic cells. Nerve fibers lie 

 parallel with the outer dorsal surface quite similar to the nerve 

 fibers in other pineal organs. These are probably the nerve 

 fibers which constitute the tractus pinealis. Klinckowstroem 207 

 in 1893 found cilia on the cells of the pineal organ in embryos 

 of Iguana and Tejus, but not in the adults of these species. 

 Pigmentation is either entirely absent in all parts of the pineal 

 organ or when present it is in the interior of the cylindrical 

 cells placed in the lumen. A tractus pinealis was described by 

 Leydig 239 in 1896 in Platydactylus. Melchers, however, 269 in 1899, 

 showed these fibers were probably connective tissue. Saurians, 

 as a rule, although they do not in every case present a well- 



