580 
Proceedings of Royal Society of Edinburgh. [sess.. 
(27) Spencer, W. B., “ On the Presence and Structure of the 
Pineal Eye in Lacertilia,” Quart. Jour. Micr. Sci., vol. xxvii., 1887, 
p. 165. 
(28) Spencer, W. B., “ The Parietal Eye of Hatteria,” Nature , 
vol. xxxiv., 1886, p. 33. 
(29) Spencer, W. B., “Preliminary Communication on the 
Structure and Presence in Sphenodon and other Lizards of the 
Median Eye described by von Graaf in Angius Fragilis,” Proc. of 
the Roy. Soc., 1886, p. 559. 
(30) Thomas, A. P. W., “Preliminary Note on the Development 
of the Tuatara (Sphenodon Punctatus), Proc. of the Roy. Soc., vol. 
xlviii., 1890, p. 152. 
Y. Explanation of the Figures. 
[All the figures were drawn with the aid of the camera lucida (Zeiss) and 
Zeiss’ objective A, except figure 9, which was drawn with Zeiss’ objective D.] 
Ep. Ev., epiphysial evagination ; Ep. R., epiphysial recesses 
F. B., fore-brain cavity ; p., pigment ; r., roof of fore-brain. The 
letters R. and L. indicate the right and left sides of the brain 
respectively. 
Fig. 1 is a transverse section through the roof of the fore-brain 
of a 4 mm. frog-tadpole (ten days after fertilisation; previous to 
hatching) ; the two epiphysial recesses are shown, of which the 
right is the larger of the two. The pigment lining the recesses is 
also well seen. The plane of section has passed through the brain- 
roof in a rather slanting direction, and this has caused the section 
to appear thicker than is actually the case. Embryo No. 2. 
Fig. 2 is from a somewhat older frog-tadpole (6 mm. long ; twelve 
days after fertilisation). There is now only one recess present, and 
its opening is situated to the left of the middle line. Within this 
recess there is just the suggestion of the presence of two smaller 
recesses, and these may represent the two primary recesses. The 
pigment is still well marked. Embryo No. 8. The degree of 
magnification is somewhat greater here. 
Fig. 3 is drawn from a toad-tadpole (4 ’5 mm. long ; ten days after’ 
fertilisation). Two small recesses are seen as in the case of the 
