124 FREDERICK TILNEY AND LUTHER F. WARREN 



trabeculae of connective tissue extend inward toward the center 

 of the organ from the capsule. The cellular elements are for 

 the most part ependymal cells and neuroglia. No ganglionic 

 cells and no nerve fibers were observed. There is no clear 

 evidence of secretory function in the epiphysis of Chelonia. The 

 organ contains a small cavity. 



In Crocodilia, the pineal organ, according to Sorensen ('94), 363 

 as well as the other elements of the epiphyseal complex, is en- 

 tirely absent. In the roof of the interbrain there is a well 

 marked commissura habenularis and a posterior commissure 

 with possibly a dorsal sac and a paraphysis. Voeltzkow 410 in 

 1903 found no epiphysis in Crocodilus madagascariensis. Rabl- 

 Riickhard 316 in 1878 showed in Alligator mississippiensis a 

 long, rounded conarium. This observation, according to later 

 observers, is probably an error, the paraphysis and chorioid 

 plexus having been mistaken for the pineal body. 



The parietal eye in Reptilia. The parapineal element in 

 saurians and sphenodon gives rise to what is known as the 

 third or parietal eye of reptiles. Among the saurians it is not 

 universally present. Its absence has been noted in certain of 

 the Geckonidae, as for example, Hemidactylus, Gehyra, Gecko, 

 and Platydactylus. It is also absent in certain Agamidae, such 

 as Draco, Ceratophora, Lyriocephalus, and Moloch. It has not 

 been observed in Tejus and Cyclodus. The general form of the 

 parietal eye is saccular with the upper wall corresponding to a 

 lens which is pigment free while the under or ventral wall which 

 corresponds to the retina is deeply pigmented. The third eye 

 presents several different forms in the different species: 



1. It may be pyriform, as is the case in Sphenodon, Spencer 366 

 and Leydig, 236 and Iguana, Spencer. 367 It is also of this shape in 

 Varanus nebulosus and Anguis, Hanitsch, 169 also in Pseudopus 

 pallasi, Studnicka. 386 



2. Dorsoventrally elongated and ovoid as in Anolis and 

 Lyriocephalus, Spencer. 367 



3. Spherical or hemispherical, in which latter case the lens is 

 flattened, as in Lacerta ocellata, Chameleon, Grammatophora 

 barbata, Moloch horridus, and Agama hispida, Leydig 238 and 

 Spencer. 368 





