JIYTIUD^.— THE MUSSEL. 



matter, which, gradually condensing, assnnies a brown- 

 isli tint, and forms a solid envelope, with two small 

 apertures for the passage of the syphon tubes. Iii 

 three days this envelope acquires a complete solidity; 

 it is the initial stage of the duly-organized tube in 

 which the animal is to accomplish its full development. 

 Beneath this opaque screen the minute miner is secure 

 from observation ; but should it be opened after a few 

 days, tlie observer will find that it has already secreted 

 a new shell, larger and more solid than the original — 

 the shell of the adult mollusc. 



The young Teredo, feeding on the debris of the wood, 

 iucreases rapidlj' ; it passes from a spheroid to an 

 elongated form, and when its body can no longer be 

 confined within the shell, projects beyond its edge, and 

 would be naked but for the covering nffurded by its 

 membranous sheath, which adheres to tho sides of the 

 ligneous dwelling-place of the animal. 



If the manner in which the Pholas executed its 

 iistonisliing operations was long a puzzle to the natu- 

 ralist, an even greater degree of mystery has always 

 surrounded the destructive processes of the Teredo. It 

 cannot perforate, or its shell would exhibit — which it 

 <loes not — some signs of friction ; it does not bore, for 

 its muscular apparatus is not adapted to rotary action. 



By way of explanation of this phenomenon, some 

 naturalists have suggested that the animal secretes a 

 liquid capable of dissolving tlie ligneous fibre. But 

 M. de Quatrefages replies that, in whatever way the 

 timber may be attacked, whether the gallery rims 

 jiarallel to or cuts across the grain of the wood, the 

 groove is always cut as accuiaiely and neati}' as if 

 dune by the sharpest tool ; whereas, bad a corroding 

 solvent been made use of, the effect would have been 

 imequal on the harder and softer portions. His own 

 hypothesis seems more felicitous. " Let us not forget," 

 he says, " that the interior of the gallery is continually 

 saturated with water : consequently, all the points of 

 the wall not protected, by the animal's sheath are 

 exposed to incessant maceration. In this state, a 

 mechanical action, even if ver}' inconsiderable, would 

 suffice to clear away the bed of fibre thus softened; and 

 if this action be in any degree continuous, it suffices 

 to explain the construction of the galleries, however 

 extensively tlioy may ramify. To me, the upper 

 cutaneous folds, especially the cephalic hood already 

 referred to, since they possess the power of expanding 

 freely under an aflhix of blood, while they are covered 

 with a thick, leathery epidermis and moved by four 

 strong muscles, seem to me very capable of accom- 

 ]'lishing this operation. It does not appear improbable 

 that this hood may be charged with the removal of 

 the woody fibre, rendered incapable of resistance by 

 previous maceration, which may also be assisted by 

 some secretion from the animal." 



A singular animal, which may fitly be mentioned in 

 this category, is the Watering-pot {Aspergillum). In 

 this genus tho shell has the form of an elongated cone, 

 terminating at the larger end in a disc pierced witli 

 numerous minute tubular holes, of which the outer row 

 are the largest, forming a kind of ray or fringe around 

 it. A peculiarity of its structure is the jiresence of 

 two small valves in its conical sheath, incorporated in 



its substance, but bearing a very small resemblance to 

 it. " They there form the stamp," says Owen, " of 

 its true affinities, but subserve as little any ordinary 

 final purpose as the teeth buried in the gums of the 

 foetal whale. They have, however, enabled our natu- 

 ralists to range the animal possessing them with the 

 Tithicola, and to include them among lamellibranchiate 

 conchifcrous Mollusca. 



Shells of this genus are rare, though a great number 

 of species have been distinguished. They inhabit 

 the Red Sea, and the waters of Australia and Java. 

 Generally they bear a whitish or yellowish hue; in 

 some the tube is incrusted with a glutinatcd sand, 

 mixed wiili fragments of vari-coloured shells. Nothing 

 is known of their habits. 



THE MUSSEL. 



Mi/lilidce. — A cephalous Mulluscs. 



The Mussel, says Fredol, has neither the exq\iisite 

 taste nor the reputation of the oyster. The latter is 

 justly esteemed the very prince of shell-fi.<h, the sove- 

 reign, par excellence, of molluscs. It is the bivalve of 

 the aristocracy [nohilissimus cihus). 



Yet, let US not despise the modest mussel. Its 

 plentifulness and its cheapness render it accessible to the 

 poorest classes; it may therefore be regarded, next to 

 the chrisne, as the bivalve of the poor {rilissimiis clbus). 



The mussel may be distinguislied from all other shell- 

 fish by the azure violet tint of its valves, and the 

 yellowish red of its viscera. The oj'ster is not so gaily 

 adorned, either externall}' or internally. It wears no 

 resplendent garb, though it cruslies its rival by the 

 superiority of its more solid and lasting qualities. 



The mussel, moreover, is distinguished by its figure, 

 its food, and its beard or bj'ssus. 



1. Its delta-like figure is not without elegance. Its 

 valves are equal, longitudinal, curved, and nearly 

 triangular. One of the sides of the sharp angle form 

 the binge, where, in a deep furrow, is lodged a narrow 

 and elongated ligament. The anterior portion of the 

 mussel occupies the sharp angle. 



2. The pretended foot of this mollusc is organized 

 like a little finger. It is sometimes a couple of inches 

 in length, and hollowed by a longitudinal furrow. It 

 is an organ of touch, rather than of locomotion. From 

 this point of view, the mussel is more favoured than the 

 oyster, and, if it possesses a keener sense of touch, 

 must be gifted with a higher intelligence. 



This diHerence, perhaps, explains the old proverbial 

 saying, " stupid as an oyster," for one never says, 

 "stupid as a mussel." 



3. The byssus is an assembl.ige of small, divergent, 

 silky threads, by which the mussel attaches itself to its 

 rock with so much tenacity that not even a tempest 

 can shake its hold. It is more difficult to loosen its 

 grasp than to break its shell. 



The gland that secretes the byssus is situated near 

 the base of the foot. It emerges at first in a semi- 

 liquid stale — a viscous fl'iid, which is organized and 



