238 W. BALDWIN SPENOEE. 



EiG. 30. — Longitudinal vertical section through the pineal eye of Lacerta 

 ocellata, showing the double nature of the nerve. 



Fig. 31. — Diagrammatic longitudinal vertical section through the brain of 

 Calotes ophiomaca, to show the pineal eye lying within the parietal 

 foramen and its relationship to the epiphysis, and of this to the brain. 



Fig. 32. — Longitudinal vertical section through the pineal eye of Seps 

 chalcidica, showing its relationship to the foramen and its surrounding of 

 deep pigment. 



Fig. 33. — Longitudinal vertical section through the pineal eye of Calotes 

 ophiomaca, showing its relationship to the parietal foramen and the blood- 

 vessel within the latter. 



PLATE XIX. 



Fig. 34. — Diagrammatic longitudinal vertical section through the parietal 

 foramen of Varanus giganteus, showing the eye within the parietal fora- 

 men and the pineal stalk. 



Fig. 35. — Diagrammatic longitudinal vertical section through the median 

 line of the brain of Plica umbra, to show the eye and its relationship to 

 the pineal stalk and epiphysis. 



Fig. 36. — Diagrammatic side view of the brain and pineal eye ot Moloch 

 horridus, viewed as a solid object, the eye lying within the parietal foramen. 



Fig. 37. — Modified median eye-scale of a small Varanus bengalensis. 



Fig. 38. — Modified median eye-scale of Leiodera nitida. 



Fig, 39. — Modified median eyerscale of Agama hispida. 



Fig. 40. — Diagrammatic longitudinal vertical section through the brain of 

 Chameleo vulgaris, to show the distal vesicle with the pineal stalk. 



Fig. 41. — Diagrammatic longitudinal vertical section through the brain of 

 Varanus bengalensis, showing the eye lying in the parietal foramen, and 

 the pineal stalk with its swollen extremity beneath the eye, 



PLATE XX. 



Diagram illustrating the development of the epiphysis from an internally 

 placed eye in the " brain " of an ancestor common to Tuuicata and higher 

 Chordata. Figs. 1 — 7 illustrate the evolution of the organ till its highest 

 stage of development is reached. Figs. 2 and 3 are diagrammatised from 

 those of two stages in the development of the epiphysis in Bufo cinerea, 

 as given by de Graaf, Fig. 1 represents an early stage of development, accord- 

 ing to Kowalevsky, iu Tunicates, before the formation of a lens. In higher 

 Chordata loss of pigment and evagination produce the epiphysis, which may 

 in various forms reach different stages shown in the figures. The cross-line 

 shading indicates the parietal bone. Figs. 9 — 12 representing various stages 

 of degeneration in forms in which the parietal foramen becomes closed, AU 

 the figures are, of course, perfectly diagrammatical. 



