contain the whole lobster, which, in his borrowed panoply, now walks abroad in safety, careless of the wave and regardless of an enemy; for, on the least alarm, he retreats rapidly within his adopted house, where he is secure from all ordinary shocks and assailants. The small shells become the home of the young Paguri; but when the lobsters have grown too large to be contained easily in the cavity, they quit it to occupy a larger, and their combats with one another to obtain the shell of their choice has been a favourite theme with popular writers and voyagers, for they are very common on the shores of all countries.* That this connection between the lobster and the shell is not accidental but foreordained, is clear from the structure of the former: at the extremity of the tail there are some appendages curved, and otherwise fashioned, in a manner which shews that they were made to hold to the shell; and on that side of the posterior half of the body which is applied against the pillar of the shell, there is a series of similar appendages or claspers, which, let it be remarked, occur on that side only, while all other lobsters are symmetrical or alike on both halves. To these particulars permit me to add the following passage from a paper on the habits of Paguri by Mr. Broderip:-"In pursuing my inquiries upon this subject," he says, "I have been struck by two beautiful provisions in the animal oeconomy of these Paguri. Their backs are towards the arch of the shell, and their well-armed nippers and first two pair of feet generally project beyond the mouth of it. Their two short pair of feet rest upon the polished surface of the columella, and the outer surface of their termination, especially that of the first pair, is most admirably rough-shod to give the soldier' a firm footing when he makes his sortie, or to add to the resistance of the crustaceous holders at the end of his tail when he is attacked and wishes to withdraw into his castle. On passing the finger downwards over the termination of the feet they feel smooth; but if the finger be passed upwards the roughness is instantly perceived. The same sort of structure (it is as rough as a file) is to be seen in the two smaller caudal holders. The second provision I observed in a very fine and large species of Pagurus from the Mauritius. Two specimens are in my possession; one of which is housed in a very large young shell of Pteroceras truncatum, the other (nearly a foot long) is naked, and on examining the under side of * Our native Pagurus bernhardus, adapts itself readily to many kinds of shells, but it is asserted that some foreign Paguri use only certain species of univalves. Some small native Paguri, recently discovered, seem to be also limited in their choice.-See BELL's Brit. Crustacea, pp. 171-187. the tail of this, a great number of transverse rows of acetabula are to be seen even without the aid of a glass. My friend, Dr. Bright, has another naked specimen in which the same formation, which must very much assist the hold of the Pagurus, is visible."* There is something so uncommon and wonderful in this adoption of the shell of one animal by another, to favour which even an anomalism of structure was requisite, that the great Swammerdam, familiar as he was with all the miraculous phenomena of insect life, could never credit the history, believing that the lobster was the true original tenant. "Hence it appears what an idle fable that is which is etablished even amongst those who study shellfishes, when they shew some of the crab kind in their museums, adding at the same time, that they pass from one shell to another, devour the animals that lived in those shells, and keep them for their own habitations. They dignify them with sounding names and additions, as soldiers, hermits, and the like; and thus, having no experience, they commit gross errors, and deceive themselves as well as others with their idle imaginations." It is, however, the very reverse of an idle fable; and here allow me to add that I know of no one fact which more directly negatives all the strange hypotheses which have been of late years broached relative to the capabilities of animals to alter their forms and go forward to perfectibility; for, assuredly, no animal coated, as the lobster is, with a crust fitted with the nicest adaptation would yearn to free itself of this mail and expose its thin skin to the rude elements; or, having done this folly, would not, were it able, by a continual desire and consequent reflux of its fluids, regenerate its own crust rather than thrust its naked tail, from race to race, into a shell which is comparatively a cumbersome appliance, and not more neatly fitted to its bulk than were the boots of the heavy dragoon to the uncalfed legs of the famous Goose Gibby! The animal most nearly allied to the Hermit-lobster which uses a somewhat similar device is a native species of spider, whose operations I have had the pleasure of witnessing. This insect lives habitually in and under water; but having really no fellowship with that element, in which it can neither live nor breathe like aquatic animals, that it may pass its life there in a dry comfortable manner, it appropriates to its use the old shells of water-snails (Limnæus stagnalis). Entering the shell, the spider closes the aperture with a web or curtain of varnished silk, which repels the water and hinders its + Book of Nature, 66. * Zool. Journ. iv. 207. admission; she then fills her abode with atmospherical air, but how I am not able to say. The shell is sometimes found lying at the bottom of the pond, but, rendered buoyant by the air within, it often rises and floats on the surface, and the wily insect is in this manner carried within reach of her prey, who feel no alarm on the approach of what seems a snail! The stratagem reminds us of the sportsman, who, in some of the fenny counties of England, lies hidden in a shallow boat, and permits himself to be carried by the winds or current amid his unsuspecting game. * There is a genus of naked worms (Siphunculus) which makes a similar use of dead molluscous shells. One species, discovered by Mr. Montagu, inhabits old worn specimens of the Strombus pespelicani and Turritella cornea, whose apertures it closes with sand cemented by a glairy secretion, leaving only a small circular hole sufficient for the protrusion of its long proboscis, but incapable of admitting any animal by which its safety can be endangered. Another species, common on our northern shores, takes possession of the common tooth-shell (Dentalium entalis), securing the aperture in the same manner; and there are foreign species which exhibit analogous artifices. Other soft worms and zoophytes (Cliona celata) penetrate the substance of shells, boring deep furrows in them, where they safely follow out their life and prescribed duty; and let it be remembered, that these worms are always constructed with a reference to the shells which they dig into: though the mollusk is independent of them, they, on the contrary, are entirely dependent on the mollusk. There is not the same intimate dependence between some land-shells and some insects that appropriate them; but the instinct that leads the insects to this appropriation is worth noticing. Two nearly allied to the Bee form their nests in the deserted shells of snails; one of them (Osmya bicolor) apparently nidifies only in the Helix nemoralis, and the other (Osmya helicicola) most frequently in the Helix pomatia. Another insect, named Sopyga punctata, inhabits the same shells, and passes its two stages of metamorphoses in the cells of the Osmya.† You might think me forgetful were I to conclude this letter without some mention of the Paper Nautilus or Argonaute, a shell familiar as the ornament of the chimney-piece, * I may not find a fitter place than this to mention that the helmet of the frogs, in the War of the Frogs and Mice, is very cleverly shown by Menke to be the Limnæus stagnalis.-Reports on Zoology, p. 417. Lond. 1847. The Naturalist, No. iii. p. 144. and as the original whence artists have derived many a pretty design for the car in which the sea-born Venus is made to ride the ocean: "A shell of ample size and light, For you must have read in some of our popular works, that the animal found in this shell has been supposed by many of our best naturalists to be, not its own fabricator and rightful owner, but an alien and vagrant cephalopod, which has had the good taste to select it for its house and canoe, probably after having made a meal of its hypothetical inhabitThis opinion, which has had advocates even from the days of Aristotle, has been maintained with much ingenious argument, and some continue to think the question unsettled; but I must confess that the perusal of Madame ant. * Of this number is Mr. J. E. Gray, who, in a very recent publication, has summed up the most important arguments in favour of the animal's parasitism in the following passage:-"The female Ocythoes are often found in the shell of the Argonaut, and have hence been supposed to form these shells, and as yet no other animal has been found inhabiting them; but there are several reasons for believing that the Ocythoe is only a parasite adapted by its form to live in such shells, as the web of the arms is used by the animal to embrace the shell and keep it in its right position on the body. Unlike all other mollusca, which form the shell they inhabit: First, the Ocythoe is not attached to the shell by any muscle, nor has it any muscle, like the bone-bearing cuttle-fish, formed for the purpose of attaching the body to its internal shell. Secondly, the animal, when alive, does not fit the shell; so that the shell cannot have been moulded on its body, as in other mollusca. Thirdly, the skin of the Ocythoe is of the same texture and appearance as in the other naked cephalopoda; and the presence of sand between the shell and the body appears to cause no uneasiness to the animal, as it does in all other shell-bearing mollusca, where the animal immediately rids itself of the irritation so caused by covering the sand, &c., with a calcareous coat. The animals found in these shells are always female, and the apex of the shell is filled with very small eggs; while from the large size of the young shell, which is seen on the apex the true Argonaut, we should expect the animal which formed that shell to have a large egg; for, though the eggs of mollusca are enlarged during the hatching, they are not, in any case I have observed, so much enlarged as to have such a shell. of "It is supposed by the persons who believe that the shell is formed by the Ocythoe, that it is formed and mended when broken by the expanded ends of the upper arms, which embrace the outer surface of the shell, and thus keep it on the body of the animal. "Cranch and Adams, who have seen these animals alive, state that they leave the shell when they are frightened, and that they cannot recover their position in the shell after they have thus left it. "Mr. Adams regards the Argonaut shell as a nest formed by the female to contain her eggs; so, if this is correct, they can scarcely be compared to other shells. He regards them as similar to the cartilaginous cases which Murices and other zoophagous mollusca form to contain their eggs; but Power's experiments, supported as they are in the main by those of Sander Rang; and a study of Professor Owen's ably reasoned report on them, and on the opposing facts, have convinced me of its erroneousness; and now I believe the shell and the cephalopod to be one species and individual, whose curious history will occupy us in a future letter. they have no apparent analogy to those bodies, which are secreted by the oviduct as the eggs are deposited. "These various views shew that the origin of the shell is not yet distinctly settled."-Catalogue of Cephalopoda in Brit. Mus. 28. The reader will find the various papers alluded to in the first and third volumes of Charlesworth's Mag. of Nat. History, and in the Notices of Communications to the British Association for the Advancement of Science, 1844, p. 74. |