But this is not all. Again, look at the living Sea-Urchin. It bristles
with the rosy-tipped spines, which have a satiny lustre, owing to the
reflection of the light from the delicate ridges and furrows with
which the whole is fluted, like an Ionic column in miniature. How
they are all moving, and swaying to and fro on their bases, quite
independently of each other, however, making circles and traverses in
the water with their points, as the mast-heads of a ship do among the
clouds in a gentle swell, when seen from the deck. Professor Agassiz
fell into the egregious blunder of supposing that the spines were the
organs of locomotion in the Urchins, denying, with much contempt, the
theory which attributed this office to the suckers. One can only wonder
whether he ever saw a living Urchin in motion, as one moment’s glance
at the phenomenon is sufficient to prove how utterly his theory was
false, as Forbes has well shown.
However, let us once more observe the empty denuded box from the
cabinet; and now on the exterior. Between the principal bands of pores
(called _ambulacra_, from their fancied resemblance to walks in a
garden), as also between the two series which constitute each band, the
space is studded with hemispherical warts, of very diverse size, which
look as if turned in ivory, unpolished; and each wart is crowned with
a smaller wart of like material, but bearing the most perfect polish.
At the bottom of each spine there is a cavity exactly fitting this
second wart, and equally highly-polished in its interior. During life
the spine was seated on the wart, not united to it, but moving upon
it in all directions, with perfect smoothness and freedom; a ball and
socket joint, in fact. It was held in its place by an investment of
muscle, which completely enclosed both the wart and the base of the
spine, having one insertion in the unpolished wart, and the other in a
remarkable ring or shoulder of the spine, visible just above the socket.
These are but two or three salient points of interest in the structure
of this little unvalued, disregarded creature. I could relate much
more; indeed, I think it would not be difficult to write a bulky volume
of the history and biography of a single Sea-Urchin, of which every
page would display the glory of God. But I have not space for that here.
We sometimes, but very rarely, find on this coast a very lovely form
of this class of animals, the Rosy Feather-star.[90] It consists of
ten long attenuated arms, radiating from a common centre, composed
each of about forty slender joints of stone, and each joint carrying a
pair of diverging beards, also many-jointed, all of which together, by
their number and arrangement, give to the arm the aspect of a beautiful
feather. Around the central point of radiation, a small cup-like body
gives origin to the arms, which are double, a pair springing from
a single basal joint. Within the cup the soft parts of the animal
are chiefly located, the organs of the vital functions; and from
the convex surface spring a number of jointed stony threads, like
necklaces, much shorter and slenderer than the arms, which serve as
claspers, gripping and holding firmly the projections of the rock, by
means of strong curved claws with which they are terminated, in shape
like those of an eagle.
The whole elegant creature is of a lively rose tint, interrupted by
patches of bright yellow, disposed with no regularity or apparent
order; the whole, both the yellow and the rosy portions, studded with
crimson dots. Edward Forbes, if I rightly understand him, considers
these dots to be ovaries, which he estimates at upwards of 57,000 in
number.