THE PINEAL EOD\ 31 



this structure and the end-vesicle. The latter constitutes the 

 cutaneous gland. These two parts, connected by a stalk of fine 

 fibers which lead to the brain roof as the tractus pinealis, are the 

 distinguishing features of this region in Anura. The proximal 

 part alone in Anura is the homologue of the very rudimentary 

 organs observed in Urodela. The pineal organ of the frog's 

 brain has often been mistaken for the highly developed chorioid 

 plexus, for the paraphysis, or for the dorsal sac. Such errors 

 have been made by Wymann 431 in 1853, Reissner 328 in 1864, and 

 Stieda 379 in 1875. Goette 151 in 1873 first recognized the proximal 

 portion of the pineal organ and called it the epiphysis. This he 

 observed in the early stages of development in Bombinator. 

 Gravenhearst 158 many years before this found the distal part of 

 the pineal organ in the head of Rana subsaltans, situated in 

 relation to a light colored spot on the skin over the head. Reiss- 

 ner 328 also noted a similar spot. Stieda called this spot the 

 Scheitelfleck (parietal spot). To this spot he gave an inter- 

 pretation of much interest, for he believed that it marked the 

 situation of a peculiar, subcutaneous frontal gland directly under 

 the skin and this gland, therefore, became known as the frontal 

 subcutaneous gland of Stieda. A fine, thread-like structure led 

 from the skull to this gland and thus connected them. Ciaccio 65 

 in 1867, following Stieda's lead, placed this structure among the 

 so-called nerve glands of Luschka. Leydig 233 in 1856 considered 

 the organ merely as a skin gland, but Goette 151 in 1873-75 studied 

 the epiphysis developmentally and stated that the subcutaneous 

 frontal gland was nothing more than the detached distal end of 

 the epiphysis. 



The pineal region in amphibia, generally speaking, comprises 

 the following structures: The lamina supraneuroporica, which 

 is a short and thick end wall of the forebrain. The next and, 

 perhaps, most conspicuous element of the pineal region in am- 

 phibia is the massive and vascular paraphysis which, according 

 to certain authorities, reaches its highest development in these 

 forms. It has all the characteristics of a tubular gland with a 

 definite sinusoidal circulation and a canal which connects it with 

 the ventricles of the brain. The velum transversum is short 



