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of vision. With the latter cells they remained connected by proto 
plasmic filaments, and thus they came to form a thickening of the 
epidermis underneath the organ of vision, the cells of which received 
their stimuli from those of the organ of vision and transmitted the 
stimuli so received to other parts of the body. . . . Such a thicken 
ing would obviously be the rudiment of a central nervous system. 
. . . It is easy to see by what steps it might become larger and 
more important, and might gradually travel inwards, remaining 
connected with the sense organ at the surface by protoplasmic 
filaments which would then constitute nerves. The rudimentary eye 
would at first merely consist of cells sensitive to light, and of ganglion- 
cells connected with them ; while at a later period optical structures, 
constituting a lens capable of throwing an image of external objects 
upon it, would be developed, and so convert the whole structure into 
a true organ of vision.”—(A Treatise on Comparative Embryology, 
vol. ii., pp. 401-402.) 
“All the (auditory) organs have their origin in specialised portions 
of the epidermis. Some of the cells of a special region become 
provided at their free extremities with peculiar hairs known as 
auditory hairs ; while in other cells concretions known as otoliths are 
formed, which appear often to be sufficiently free to be acted upon by 
vibrations of the surrounding medium, and to be so placed as to be 
able, in their turn, to transmit their vibrations to the cells with 
auditory hairs.”—{Ibid. p. 512.) 
“ It seems quite possible that many of the epithelial cells of the 
epidermis and w r alls of the alimentary tract were originally provided 
with processes the protoplasm of which, like that of the Protozoa, 
carried on the functions of nerves and muscles at the same time, and 
that these processes united amongst themselves into a network. . . . 
By a subsequent differentiation some of the cells forming this network 
may have become specially contractile, the epithelial parts of the cells 
ceasing to have a nervous function, and other cells may have lost 
their contractility and become solely nervous.”—{Ibid. p. 40J.) 
Natural Selection does not account for the fact that 
certain cells became more sensitive to light than the rest 
of the surface cells : all that its supporters can say is 
that if this difference arose in some, and if it was very 
advantageous to its possessors, they would survive and the 
rest would perish. And the same is true of the pigment 
cell, the otolith, and the differentiation into nerve and 
muscle. On the other hand, it seems to me that if