PARIKTAL EYE AND ADJACENT ORGANS IN SPHENODON. 158 



adherent humour containing a nucleus, and witii another nucleus apparently 

 escaping from the under surface of the lens. Zeiss F, oc. 1, camera outline. 



Fig. 20. — Stage O. Embryo 92. Part of wall of parietal stalk from same 

 section as last, with adhering humour and nucleus. Zeiss F, oc. 1, camera 

 outline. 



Fig. 21. — Stage R (late). Embryo 3. Transverse section through the 

 parietal stalk near its distal extremity. Zeiss D, oc. 1, camera outline. 



Figs. 22 — 27. — Stage R (late). Embryo 3. Transverse sections through 

 the third ventricle and adjacent parts, arranged in order from before back- 

 wards. X 16^. Camera outlines. 



Fig. 28. — Hinulia, sp. Part of a sagittal section through the third 

 ventricle and adjacent parts of an advanced embryo, to show the relations 

 of the "epiphysis," parietal eye, and associated parts. Zeiss A, oc. 1. 

 Slightly diagrammatic. 



