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since it could no longer destroy the wood in which it was 

 contained. Sir Everard however remarks that in Teredo 

 giguntea death is not a consequence of seclusion from the 

 substance in which it is imbedded. In some of Mr. Grif- 

 fiths's specimens the shell was just covered in, and the 

 part close to the termination extremely thin, whilst in 

 others it was increased twenty-fold in thickness. In others 

 again the shell had not only become thick, but the animal 

 had receded from its first inclosure, and had formed a 

 second three inches up the tube, and afterwards a third 

 two inches further on, and had made the sides thicker and 

 thicker, so as to diminish the canal in proportion to the 

 diminution of its own size. 



Animal of Teredo navalis out of the shell. 



1. the opercula are wanting, and the tubes retracted. 2. the opcrcula in their 

 situation, and the tut>e protrudfl a, a, the boring-shells; 6. the proboscis; 

 f, tlte mouth ; d. d, the contf nls of the aldomen seen through the tr tnsnarent 

 external covering ; e, c, breathing organs seen in the same way. (Phil. Trans.) 



Sir Everard considers these facts as proving that Teredo 

 gigantea, when arrived at its full growth, or whenever it 

 is prevented from increasing in length, closes up the end 

 of its shell, and lives a long time afterwards, furnished 

 with food from the sea-water. Teredo navalis, he observes, 

 m up its shell in the same manner : it must therefore, 

 after that period, be supplied with food entirely through 

 the medium of sea-water. The Teredines, he adds, turn 

 round in the shell, to which they are not attached, and 

 with which their covering only has a slight connection at 

 one particular spot, to prevent the external tubes from 

 being disturbed. This motion, Sir Everard observes, is for 

 the purpose of boring. 



Geneve Character. Animal very much elongated, ver- 

 miform, with a very delicate mantle, open in front and at 

 its lower part for the passage of a mammiliform foot ; 

 tubes separated, very short, especially that for the dejec- 

 tions; mouth small ; labial appendages short ; anus situ- 

 ated at the extremity of a small tube floating in the cavity 

 of the mantle ; branchiae riband-like, united on the same 

 line throughout their length, and a little prolonged in the 

 siphon ; a muscular ring at the point of junction of the 

 mantle and the tubes, in which is implanted a pair of 

 pedieulated corneo-calcareous appendages or palmules, 

 playine laterally one against the other. 



Mirll rather thick, very short, annular, equally open 

 before and behind; equivalve, inequilateral, angular, with 

 triangular valves, trenchant in front, and only touching 

 each other by the two opposite edges ; no hinge ; an elon- 

 gated, nearly straight, siibfiliform, spoon-shaped process; 

 a single Bligntly-ravked muscular impression. 



Tube oyfindrical, straight or fk'xuous, closed with age 

 at the buccal extremity, so as to envelope the animal and 

 its shell, always open at the other, and lining the cavity 

 into which tin- animal has introduced itself. 



Such is M. Kang's definition of Teredo, excluding Teredo 

 Septaria\ of which he pvei the following de- 

 ing that it closely approximates to the 



.- 



unknown. (But see the paper of M. Mathtron 

 above referred to.) 



unknown. (But see the descriptions of Mr. Grif- 

 .il Sir Everard Home here noticed.) 

 Tube calcareous, thick, solid, in the shape of a very 

 elongated cone, nml irregularly flexuous, furnished inter- 

 nally with small, incomplete, annuliform septa ; terminated 

 at one of its extremities by a convexity, and at the other 

 by two slender and separated tubes. 



The i! . oi TiTi'iln (exclusive of Srpfaria) 



'k in the ' Animaux sans Veil' 

 '181H; v.ere two, Teredo navalis and Teredo palmulatus : 



of the latter Lamarck, who had seen neither its tube ncr 

 its shell, says that it probably only differs from Teredo na- 

 valis in its greater size, its longer palmules having been 

 more easily observed. 



M. Deshayes, in his Tables, makes the number five living 

 and five fossil (tertiary), exclusive of Septaria ; and, in 

 the last edition of Lamarck, adds to the two species above 

 noticed Teredo corniJormis(Fistulanacorniformis, Lam.), 

 Teredo gregatus (Fistulana gregata. Lain.), and Teredo 

 arenarhts (Septaria arenaria, Lam.). 



N.B. Lamarck had stated that the Ropan of^Adanson 

 (Senegal, pi. 19, f. 2) belonged to the Teredines, remark- 

 ing however that he (Lamarck) knew it not. But M. 

 Deshayes points out that M. Rang, on his return from a 

 voyage to Senegal, where he had an opportunity of ob- 

 serving ihe Ropan, found that this curious shell belonged 

 neither to the Teredines, as Lamarck believed, nor to the 

 Pholades, as Bosc says, and still less to the Gastrochcence, 

 as M. de Blainville supposes ; but that it is a Modiola 

 already known, Modiola caudigera. 



Teredo Navalis. This is sufficiently described above, 

 and we therefore proceed te the consideration of its 



Food, Habits, fyc. Some of the Teredines examined by 

 Sir Everard Home were sent from Sheerness in the wood 

 alive, and they lived in salt-water for three days after 

 being brought to town. Sir Everard observed that when 

 the surface of the wood was examined in a good light, 

 while only an inch in depth in the water, the animal threw 

 out sometimes one, at others two small tubes. When one 

 only was protruded, the other almost immediately followed 

 it. One of them was about three-quarters of an inch long ; 

 the other only half that size. When the largest was ex- 

 posed to its full extent, there was a fringe on the inside of 

 its external orifice of about twenty small tentaeula, scarcely 

 visible to the naked eye : these were never seen except in 

 that state ; for when the tube was retracted, the end was 

 first drawn in, and so on, until the whole was completely 

 inverted : and therefore in a half-protruded state it ap- 

 peared to have a blunt termination with a rounded edge. 

 The smaller tube was not inverted when drawn in. 'These 

 tubes,' says Sir Everard Home, in continuation, ' while 

 playing about in the water appeared at different times to 

 vary in their directions, but usually remained at the 

 greatest convenient distance from each other. The largest 

 was always the most erect, and its orifice the most dilated ; 

 the smaller one was sometimes bent on itself with its point 

 touching the wood. In one instance, where a small insect 

 came across the larger one, the point of the smaller turned 

 round and pushed it off, and then went back to its original 

 situation. In several instances the smaller one appeared 

 to be the most sensible ; since by touching the larger one 

 gently it did not retract ; but on touching the smaller one 

 they both were instantly drawn in. Indeed whenever they 

 were retracted they always were drawn in together. When 

 the worm was confined within the shell the orifice was 

 not to be distinguished in the irregular surface of the 

 wood, which was covered with small fuel. The worm ap- 

 pears commonly to bore in the direction of the grain of 

 the wood, but occasionally it bores across the grain to 

 avoid the track of any of the others ; and in some in- 

 stances there was only a semitransparent membrane as a 

 partition between two of them.' 



Sir Everard observes that as the Teredo gigantea bores 

 in mud, on which it cannot be supposed to subsist, or 

 even to receive any part of its nutriment from it, it be- 

 comes a question whether the Teredo navalis, an animal 

 of much smaller size, derives support from the wood 

 which it destroys, or in supplied wholly from the sea. 

 The last opinion seems the most probable to Sir Everard, 

 because the animal, having red blood and very perfect 

 organs, necessarily requires a great deal of nourishment for 

 the purposes of growth, and to supply the waste constantly 

 going on ; but if, he observes, the aggregate of shell and 

 animal substance is taken, it will be found equal in bulk, 

 and greater in specific gravity than the wood displaced in 

 making the hole : hence, he remarks, it is obvious that the 

 quantity of wood which the animal has taken into its body 

 K wholly insufficient for its formation and subsistence. 

 When once it is established that the Teredo can be sup- 

 ported independently of the wood which is oaten, and can 

 afterwards subsist when the communication between it and 

 the wood is cut off, a doubt, he adds, is created about the 

 wood forming any part of its aliment, and it becomes pro- 



