368 H. M. BERNARD. 
had been assumed by Lankester, he suggests that the same 
structure which, at an early stage of its development, formed 
the tunicate eye developed into the pineal eye only after it 
had grown out into a long stalked vesicle. The inherent 
objections to this supposition seem to me to be as great as 
those which it was intended to avoid. On the other hand, 
however, the facts appear to me to be all in favour of the 
account given above, the parallel between the retina with the 
retinal pigment and the palisade layer with its subjacent 
accumulation of pigment cells, between the connective-tissue 
capsule of the eye, with its chromatophores and other wan- 
dering cells, and the cutis—the fact that the eye is still em- 
bedded in the thickened cutis in many forms, and that the 
skin above the eye is frequently found transparent,—all seem 
to indicate the skin, and not the brain, as the real mother- 
tissue of the eye. 
Given, then, the possibility of explaining the embryology 
of the pineal eye as adaptive, there seems to me to be no valid 
reason why we should not accept the teachings of comparative 
morphology, and recognise the pineal eye as a relic of the 
simpler type of skin of our Invertebrate ancestors. 
The suggestion that the pineal eye arose out of detached 
portions of the paired primary optic vesicles, I think, defies all 
attempts to work out in detail. Beard’s explanatory diagrams, 
it seems to me, cease to be manageable if, instead of single 
layers of epithelial cells, we try to marshal functional eyes in 
the same way. 
In the foregoing pages I have endeavoured to show how the 
Vertebrate eyes admit of being deduced directly from the skin, 
as my theory of the origin of sight requires. My object has 
been not only to remove a possible objection to the theory 
arising from the embryological development of these eyes, but 
also to show how they might be made even to bear testimony in 
itsfavour. It must be borne in mind that the arguments here 
adopted are not so strong as they might be. They would have 
1 Beard, “‘The Parietal Eye of Cyclostomes,” ‘Quart. Journ. Micros. 
Sci.,’ vol. xxix, pl. vi, figs. A, B, C. ; 
