We will now turn for a short space to the lower divisions of the animal
kingdom. The Echinodermata (star-fishes, sea-urchins, etc.) are furnished
with remarkable organs, called pedicellariae, which consist, when well
developed, of a tridactyle forceps--that is, of one formed of three
serrated arms, neatly fitting together and placed on the summit of a
flexible stem, moved by muscles. These forceps can seize firmly hold of
any object; and Alexander Agassiz has seen an Echinus or sea-urchin rapidly
passing particles of excrement from forceps to forceps down certain lines
of its body, in order that its shell should not be fouled. But there is no
doubt that besides removing dirt of all kinds, they subserve other
functions; and one of these apparently is defence.
With respect to these organs, Mr. Mivart, as on so many previous occasions,
asks: "What would be the utility of the FIRST RUDIMENTARY BEGINNINGS of
such structures, and how could such insipient buddings have ever preserved
the life of a single Echinus?" He adds, "not even the SUDDEN development
of the snapping action would have been beneficial without the freely
movable stalk, nor could the latter have been efficient without the
snapping jaws, yet no minute, nearly indefinite variations could
simultaneously evolve these complex co-ordinations of structure; to deny
this seems to do no less than to affirm a startling paradox.
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