THE PINEAL BODY 133 



1. Evaginations of the distal end of the epiphysis as in Anguis 

 and Iguana. 



2. Independent buds off the epiphysis or extrusions from 

 it held in relation by pigment strands of cells, as in Lacerta 

 vivipara. 



3. Isolated extrusions from the end of the epiphysis. 

 Accessory parietal eye organs are less common. Carriere 57 



in 1890 showed a diverticulum from the under wall of the parietal 

 eye. Prenant 312 in 1895 made the same observation. Fran- 

 cotte 127 found that these accessories consist of a lens and retina 

 which are still in connection with the chief organ. Accessory 

 organs usually have pigment in them, but this is not so in Phry- 

 nosoma and Sphenodon. Only the under wall is pigmented as 

 a rule, so that the under wall corresponds to the retina while 

 the upper wall corresponds to the lens. Such accessory organs 

 attached to the parietal eye indicate an attempt to produce 

 another optic organ. Only exceptionally does the upper or 

 dorsal wall show a lens formation. In Pseudopus, Studnicka 384 

 in 1893 found that the interior of the accessory parietal eye con- 

 tained a syncytium as does the actual parietal eye. Prenant 312 

 in 1895 differentiated the following types of accessory organs in 

 Anguis: 



1. Epiphyseal eye. This lies close to the epiphysis, yet sepa- 

 rated from it and is entirely derived from that organ. 



2. Interparietal-epiphyseal eye. This is situated in the mid- 

 line between the epiphysis and the parietal eye. It is the most 

 frequent of the accessory parietal eye organs. 



3. Intraparietal eye. This is connected with the retina and 

 under wall of the parietal eye or else is included in it. 



4. Accessory chorioidal eye. This is found very infrequently. 

 It is widely separated from both parietal organs and presents 

 itself as a pigmented hollow vesicle lying on the upper surface 

 of the chorioid plexus. 



Accessory parietal organ structures are most frequent in 

 embryos and tend to disappear in the adult. This observation 

 is agreed to by most authors. 



