THE PINEAL BODY 33 



on the other hand, in most forms presents a less well-developed 

 appearance, and in many instances (in Lensu stricto) an epi- 

 physis cerebri alone may be observed. The parietal eye, earlier 

 but incorrectly called the pineal eye, is absent in many 

 forms even among the lower reptiles. It is undoubtedly the 

 homologue of the anterior epiphyseal organ or parapineal organ 

 of teleosts and perhaps the parapineal organ of Petromyzon. 

 No chapter in the morphology of the pineal organ is more 

 replete with interest or full of ^incentive to further research than 

 that dealing with the remarkable conditions observed in this 

 region of the brain in reptilia. From the observations on the 

 Saurians and Prosaurians have come far-reaching theories into 

 the phylogenesis of the vertebrates as well as many illuminating 

 efforts to trace the evolution of this phylum by means of the 

 unpaired parietal eye back to the invertebrates. Brandt 40 in 

 1829 was first to mention the presence of the epiphysis in the 

 Saurian brain. Milne-Edwards 107 and Duges 97 both in 1829 

 referred to certain scales in the head of Lacerta. Neither of 

 these authors described the structures, but their illustrations 

 plainly indicate that they had perceived the area in the skull in 

 which the parietal eye comes to the surface. Cuvier 77 and 

 Tiedemann 395 had both observed the organ in reptiles. Leydig 234 

 in 1872 studied the embryo of Lacerta and Anguis, giving partic- 

 ular attention to the parietal region of the skull. He described 

 a peculiar body made up of long, epithelioid, and cylindrical 

 cells. These cells were so arranged as to form a rim, the border 

 of which comprises cells of a deep black pigment. This organ 

 was not, as one might think, the epiphysis, for this latter struc- 

 ture lies distinctly above the organ described by Leydig. Ley- 

 dig, furthermore, mentioned a parietal foramen and a spot on 

 the skull indicating the position of the organ which lies beneath 

 it. This structure Leydig called the frontal organ, and while he 

 strongly suspected that it was possessed of sensory function, he 

 did not commit himself to such a theory at the time in which he 

 wrote. Strahl 382 in 1884 thought that this frontal organ of 

 Leydig had certain relations to the epiphysis and seemed able to 

 demonstrate that Leydig's organ was nothing more . than a 



MEMOIR NO. 9 



