56 



FREDERICK TILNKV AXI) LUTHER F. WARREN 



however, is the more important of the two in amphibia. Cam- 

 eron believes that there is evidence of a bilateral origin to be 

 found in the later stages of amphibian development. The 

 portion of the anlage in connection with the superior commissure 

 corresponds to the parietal eye of Sphenodon while the remainder 

 corresponds to the epiphyseal stalk. From this evidence in 

 amphibia he is inclined to agree with Dendy 86 that the ancestors 

 of vertebrates must have possessed a pair of parietal eyes (figs. 

 22 and 23). 



Fig. 21 Anlagc of the epiphyseal complex in an embryo of Triton cristatus, 

 according to dodraaf, 1886. 



('It , commissura habonularis; If., recossus and pineal organ; Cp., commissura 

 posterior; M ., midbrain; Epid., epidermis; Cor., corium. 



6. The development of the epiphyseal complex in reptilia 



The fact that in Prosanrnmx and Saurians a well deve'oped 

 eye is found in many fcrms has been the cause of much dis- 

 cussion ;is 1o the embryolgical process by means of which this 

 structure is differentiated from the epiphyseal complex. Accord- 

 ing to the older view, the p;tri<>tal eye arose, as in the case of the 

 isolated end-vesicle of amphibia, by a process of constriction 

 from the terminal portion of the pineal organ. Subsequently 

 the view was advanced that instead of a process of constriction 



