Page:Hardwicke's Science-Gossip - Volume 1.pdf/139

I had found him at last, and at home, so pounced upon him as a lawful and legitimate prize. Knife and hammer soon severed his close attachment to the rocks; and turning him up to take a peep at his powerful ring of muscle and strangely-formed breathing apparatus, I spied a worm evidently very uneasy, about three inches long, brown, and in shape like an ancient dagger-blade. He appeared to me to be wriggling out from betwixt the folds of the foot or the mantle, and apparently most anxious to escape.

My first impression was, that he was captive that by some mischance had got imprisoned under the shell of the fissurella; and thanking his lucky stars for such a fortunate deliverance, wished to make the best of his liberty, and rejoin his friends. But in displacing other shells, I found in nearly every one a similar tenant: the secret was discovered—the worm was a parasite, that lived in peace and good fellowship with Sir Keyhole,—recalling to my remembrance Ossian's lines on the Pinna and the parasitic crab—

That the parasite does no harm is clearly proved by the healthy state of the mollusc in whose shell it takes up its abode. How far mutual interest may conduce to mutual friendship, I am unable to say.

The illustration heading this article will give the reader a good idea of the Fissurella and its parasite.

On more carefully examining the position of the worm, I found it was invariably coiled away in a semicircle under the foot, like a ribbon on its edge; never flat. This seems to me a wise provision; for the pressure of the muscles when the limpet grips the rock would crush a soft-bodied worm to death if flat; but edge on, the position chosen, all risk of harm is avoided, as it fits in a cleft between two layers of soft material.

Tying several of them tightly round to prevent the worm escaping, I brought them home in situ. At least four out of every six contained a parasite, and what is rather strange, the worms were nearly all of one size. A query or two naturally suggest themselves. How did this friend or intruder, whichever it may be, first get installed as a lodger? Did he get in as a baby, and thus become an adopted child; or did he slip in as a full-grown annelide, defying Sir Keyhole to turn him out? How does he procure food; and on what does he subsist? I confess utter inability to give a satisfactory reply: my impression, however, is, the parasite grows from a minute germ (if that is a right term) in the place and position in which I found it.

I put them in sea-water, after taking them out of their sanctuary; but in no single instance did one ever go back again. I tried to replace them, but could never accomplish it, or induce the worm to remain. Not that this proves anything, inasmuch as experience teaches me any interference with the regular habits of any of the lower forms of life is at once resented; and the power, or will it may be, to adapt itself to altered circumstances is but slowly acquired. I cannot conceive the possibility of a large worm, the feet armed with curved bristles, like bundles of minute fishhooks, being quietly permitted to creep under the shell, force its way by crawling round and round the foot, by a system of hook and drag; for in no other way could it edge in, without worrying and enraging the fissurella beyond all power of endurance, ordinary pressure being only needed to squeeze the intruder flat as a pancake. By gently tickling it with a bit of sea-weed under the shell, one would say that patience was a virtue but little cultivated by the fissurella; the slightest touch, and down goes the shell with a force that cuts the weed in two like scissors. What chance would a soft-bodied worm stand? Not the slightest. The parasite, like Topsy, was "raised" where it lives.

What part a worm, doomed, as far as we know, to pass its whole life captive in the shell of a mollusc, plays on nature's wide stage, is a problem beyond human ken. We know nothing was created in vain—that the tiny diatom has its use; and this insignificant annelide serves a purpose and fulfils a destiny in the endless maze of life, as important as the lordly lion, or even man himself.

For the benefit of our scientific readers, we annex the specific description of this new parasitic worm.

Lepidonotus Lordi (Baird).—This species is about 3 inches long, and rather more than one-third of an inch in diameter at the broadest part of the body. It tapers gradually from the head to the tail, which is only about ⅛ of an inch broad. The colour is of a light brown, a broad line of a much darker brown running along the whole length of the centre of the back. On the surface, a groove runs down the centre of the body throughout its entire length. The elytra are 35 pairs in number, thin, membranous, and of a light-brown colour. The two first overlap each other slightly in the middle; but for the rest of its length the centre of the back is uncovered. The antennæ are five in number; the central one short, of much the same length as the internal ones; the two external ones the longest, white, with a bright black ring round the upper part, but leaving the point white, which is acute at the apex. The feet are tolerably stout, and the two divisions are both furnished with sharp but curved pointed bristles. The superior cirrhi are white, and of a moderate length; the inferior ones being short.