THE PINEAL BODY 119 



10. Bombinator -igneus. Leydig ('68) ; 233 deGraaf ('86). 155 In 

 this species the end-vesicle is saccular. 



In the twenty-two species of amphibia investigated, the great 

 majority present a well-developed paraphysis. In but a single 

 well-defined instance is there evidence of a tendency toward the 

 formation of a retina. This occurs in Amblystoma mexicanum 

 in which there is evidence of pigment formation in some of the 

 cells of the end-vesicle. In several forms the stalk contained 

 fibers suggestive of the pineal nerve. With reference to the 

 possible glandular character of the organ it must be borne in 

 mind that Stieda's 379 original description referred to the struc- 

 ture as the frontal subcutaneous gland. The general arrange- 

 ment of the cells, both in the end- vesicle and in the proximal 

 portion, has epithelial masses which tend to lend weight to the 

 view that the organ may have secretory function. In only one 

 instance, however, that is in Spelerpes fuscus, has there been 

 observed any definite evidence of glandular activity in the 

 pineal organ. 



6. Comparative anatomy and histology of the epiphyseal complex 



in Reptilia 



In considering the conditions present in the epiphyseal com- 

 plex of reptilia, two groups of these animals must be distin- 

 guished. The first group is that comprising the more ancient 

 reptiles, e.g., the saurians and also the prosaurians as represented 

 by Sphenodon. In the second group are the reptiles of more 

 recent history, including ophidians, chelonians and crocodilians. 

 It is in the first group, however, that the most striking appear- 

 ances are observed in the epiphyseal complex. In these forms 

 there develops a structure so remarkable for the many features 

 which identify it as a visual organ that the term parietal or 

 third eye by which it has been designated seems altogether justi- 

 fied. Quite as striking in a negative way, on the other hand, 

 are the conditions in the ophidians and in the chelonians where 

 this eye not only altogether fails, but there is no evidence 

 whatever of a parapineal organ either in adult forms or in 

 the anlage, while the pineal organ also shows marked regressive 



