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POPULAR SCIENCE REVIEW. 
integument, wliicli, in some specimens, makes a very distinct 
bulging or tumour to receive it. Indeed, the form of the organ, 
which is vertically pear-shaped or ovate, is always to be 
traced in the exterior outline. Its substance is delicately 
granular. I have not been able to trace any nerve-fibres given 
off from it ; but around the frontal expansion, just at the base 
of the arms, goes a band of substance (pi. iii.), evidently very 
different from the muscular bands, and apparently not vascular, 
which is connected by branches with another broader band, 
that passes round at the upper collar; descending branches 
and threads go from this also, and appear to pass to the walls 
of the mouth-funnel and crop. These are probably nerves. I 
suspect there is a nerve-thread, which passes centrally through 
the entire length of each arm.* 
On the upper part of the brain, and on its anterior (or 
ventral) surface, looking forward across the crop, is seated a 
minute but well-defined eye. By transmitted light it can 
scarcely be detected at all, and hence, probably, it has been 
usual to consider the organ as obliterated in infancy; but, under 
the rays of the sun, thrown on the object by means of a con- 
denser, and reflected from it, the eye comes out sharp, distinct, 
and beautifully red, as if a globule of rich opaque vermilion had 
been placed among the clear pellucid flesh. I have no difficulty 
in finding it in adult specimens, by this mode of examination. 
In the newly-hatched young there are two eye-spots. How 
these become changed into the single eye of the adult I do not 
know; I suspect by coalescence. I have, on more than one 
occasion, seen three eye-spot-s in a mature egg, of which one 
was minute, and under the others. I should have thought it 
an accidental monstrosity, but that I remarked it in two eggs. 
They were not prismatic spots, nor oil-bubbles, but globular 
specks, of opaque red, seen under sunlight, t 
The Muscular System. — In its more prominent features, 
this is very distinct. A muscular band runs round the frontal 
disk, at the base of the arms, forming a low arch, or bow, in 
the swell of each arm-base. To this annular band are attached 
strong longitudinal bands, which run through the whole length 
of the body. These are associated in pairs, running side by 
side — five pairs in all, — each pair exactly corresponding to 
an arm in direction. Each pair begins to separate at the level 
of the upper collar; and, having been connected by a short 
* See infra. 
f There is no doubt at all that the crimson specks found on the brain in 
most Rotifera are real eyes. The lens, in some species, is distinctly dis- 
cernible. 
