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POPULAR. SCIENCE REVIEW. 
I 
(‘ aqueous humour ’). On the inner wall of this chamber there 
is a layer of hexagonal plates, transparent and uncoloured, 
exhibiting a very regular concentric arrangement, and con- 
taining a protoplasmic mass which is longitudinally striated. 
These plates are looked upon by the author as representing the 
retina, and as the end- organs of nerve-fibres. 
At first sight there can be no doubt that the general cha- 
racters of an eye are very well represented, but Prof. Ley dig, 
as we shall shortly show, is able to give a very different expla- 
nation of the real meaning of these structures. 
Let us, however, next take the much more complicated case 
of Stomias (PL VI. fig. 1) ; here the ellipsoidally- shaped eyes 
are divisible into two unequal portions, the smaller of which is 
directed forwards, and is applied to the inner surface of the scales, 
while the other lies among the superficial muscles ; the two 
portions are separated by an extremely delicate partition, and the 
anterior chamber is filled by an oval and perfectly transparent 
body (/), while the posterior contains a clear and gelatinous 
substance (%), just as in the preceding case of Astronesthes ; 
the whole organ is invested by a pigmented layer ( p ), which is 
only feebly developed on the walls of the anterior chamber, and 
seems to form, though here we must say we think the re- 
semblance is pressed a little too far, a kind of iris-like dia- 
phragm (ir) between the fore and hinder divisions of the organ. 
It is curious, indeed, that hexagonal transparent cells, appa- 
rently made up of prismatic rods, should lie on the inner face 
of this coloured layer, but we must own that they hardly seem 
to us to have the distinct retinal arrangement which is assumed 
for them. 
Chauliodus is reported to have larger eye-like organs than 
the two genera already examined; but it is not necessary to 
deal in detail with this case, for it appears to us that a mere 
consideration of the account which is given of it lands us in a 
peculiarly difficult position. The arrangement of this fish's eye 
is characterized by the presence of a so-called ciliary body, 
which is described as being comparable to what obtains in the lb 
Cephalopoda. 
Here it is most necessary to be exact : are the eyes in 
question to be compared to those of other Vertebrated animals, 
or are they to be likened to those of the Invertebrata ? 
The question is not an unimportant one, for the difference || ; 
between the two is fundamental and most characteristic, far «L 
more important indeed than are most of the distinctions that BL, 
have been insisted on as justifying that most unfortunate divi- 
sion of the Animal Kingdom into the two great groups of 
Vertebrata and Invertebrata, which has for long had a disas- 
trous effect on the correct understanding of the real relations 
