Abbildungen der Seite
PDF
EPUB

the bed of the wide ocean extensive beds of oysters, clams, muscles, &c., containing millions of individuals, which are hourly devouring, each of them, crowds of animalcules (embracing in the term the infusory, microscopic, crustaceous and gelatinous medusae), which, from their vast numbers and rapid reproduction, never fail them. At some seasons of the year I have seen the waters of our shores literally in a move with Entomóstraca; and I am fully satisfied that, when Scoresby calculated a cubical mile to contain 23,888,000,000,000,000, he was not exaggerating the actual fact." In one family of bivalves furnished with a byssus, we frequently find entangled amid its fibres, or concealed within the valves, one or more small crabs (Pinnotěres), of which the older naturalists, who never left an observation to stand, like truth, all naked, but ever clothed it with some pretty vestment, tell us a tale not to be passed over in this place, and which I present you in the words of Dr. Philemon Holland, the laborious translator of Pliny. “The Nacre, also called Pinnae, is of the kind of shell fishes. It is alwaies found and caught in muddie places, but never without a companion, which they cal Pinnoter, or Pinnophylax. And it is no other but a little shrimpe, or, in some places, the smallest crab, which beareth the Nacre companie, and waites vpon him for to get some victuals. The nature of the Nacre is to gape wide, and sheweth vnto the little fishes her seelie body, without any eie at all. They come leaping by & by close vnto her; and seeing they haue good leaue, grow so hardie & bold, as to skip into her shel and fill it ful. The

* “The number of medusae in the olive-green sea was found to be immense. They were about one fourth of an inch asunder. In this proportion, a cubic inch of water must contain 64; a cubic foot, 110,592; a cubic fathom, 23,887,872; and a cubical mile about 23,888,000,000,000,000! From soundings made in the situation where these animals were found, it is probable the sea is upwards of a mile in depth; but whether these substances occupy the whole depth is uncertain. Provided, however, the depth to which they extend be but 250 fathoms, the above immense number of one species may occur in a space of two miles square. It may give a better conception of the amount of medusae in this extent, if we calculate the length of time that would be requisite, with a certain number of persons, for counting this number. Allowing that one person could count 1,000,000 in seven days, which is barely possible, it would have required that 80,000 persons should have started at the creation of the world, to complete the enumeration at the present time! — What a stupendous idea this fact gives of the immensity of creation, and of the bounty of Divine Providence, in furnishing such a profusion of life in a region so remote from the habitations of men' But if the number of animals in a space of two miles square be so great, what must be the amount requisite for the discoloration .the sea, through an extent of perhaps 20,000 or 30,000 square miles!” (Scoresby's Arctic Regions, vol. i. p. 179.)

shrimp lying in spiall, seeing this good time & opportunitie, giueth token thereof to the Nacre, secretly with a little pinch. She hath no sooner this signall, but she shuts her mouth, & whatsoever was within, crushes & kills it presently; & then she deuides the bootie with the little crab or shrimp, her sentinell and companion. I maruell therefore so much the more at them who are of opinion, that fishes and beasts in the water haue no sense.” (Vol. i. p. 261.)

Of bivalves there are some which, as I have told you, bore into wood and rocks; but I need scarcely guard you against entertaining the supposition that they eat the material on which they work, although there are authors who have attributed to them “a stone-eating power and appetite.” The Terédines, however, really eat the wood destroyed by them; for Mr. Hatchett proved the pulp in their intestine to be vegetable sawdust; but I agree with Sir E. Home in thinking that the sawdust serves only as a substance in which the real food procured from the sea is entangled and prevented from escaping too readily from the stomach. I will give you Sir Everard's description of the digestive organs (fig. 38.) of these animals, which a comparison will prove to be altogether different from those of the more typical bivalved Mollusca (fig. 37.). The æsophagus (fig. 38.* a) is now very short, and lies on the left side of the neck : the canal swells out, and becomes stomach (6), which, in its external appearance, is a large bag, extending the whole length of the cavity of the abdomen, but, when laid open, it is found to have a septum (c) dividing it

38

* This figure represents the course of the stomach and intestines of Terèdo navàlis, removed from the body. a, The æsophagus; b, the stomach; c, the septum, dividing it into two cavities; d, the aperture by which the two cavities of the stomach communicate; e, the course of the intestine to its termination. (Comp. Anat., t. 80.)

longitudinally into two equal portions, except at the lowest part, where they communicate (d), the septum being wanting. The intestine has its origin close to the termination of the oesophagus, is extremely small, dilates into a cavity containing a hard white spherical body the size of a pin's head, and then makes a turn upon itself. The course it follows is shown by the letters e in the cut. (Home's Comp. Anat., vol. i. p. 373.)

ART. IV. A Notification of the Occurrence, in the Island of Guernsey, of a Species of Testacellus, and of some of its Characteristics and Habits, as observed there. By FRedERick C. Lukis, Esq.

A species of Testacéllus is rather abundant in certain localities in this island (Guernsey); and I send drawings of it (sg. 39.) for comparison with the characteristics of T. scútu

lum Sowerby, as exhibited in the individuals of that species found, as stated in VI. 43. to 46., at Stamford Hill, Lambeth, Kensington, Bayswater, and on the side of the road from London to Hampstead; and with the characteristics of T. Maugèi, as figured in VI. 45. I avoid, purposely, applying a specific name to the species which occurs here, because I have never been able to ascertain, correctly, the distinctive differences of the few species which have been published; namely, T. haliotideus [Faure Biguet), scútulum Sowerby, Maugèi Férussac, and ambiguus Férussac, with córneus and costatus of M. de Roissy. Besides, therefore, the identification of the species represented in my drawing, information on the differential characteristics of any of the species will be very acceptable. I had hoped that the late Mr. Miller of Bristol would have made some enquiries about the species which occurs here; for

[graphic]

a

a friend of his promised, several years ago, to inform him of its inhabiting this island. In 1827, a gentleman of the Island of Jersey kindly furnished me with a shell, said to have been found in the neighbourhood of Bristol : it bore, when sent to me, a label inscribed “ Búlla haliotídea.” On my examining this shell, I found it to be that of a Testacéllus; and, as I had not seen the T. haliotídeus, which is a native of France and Spain, I imagined that some error had crept in, and that the specimen had been received from the Continent.

As far back as 1801, the Testacéllus which is represented in my drawing (fig. 39.) was known to me, as it was then plentiful in my own garden; since which period it has disappeared from it; but, at the end of the valley near which my garden is situate, the ground is plentifully supplied with individuals of it.

[Characteristics and Habits.] The colour of the animal (a) is, generally, a sickly yellow spotted with brownish specks, mixed with pale orange along the lower parts. The figure, in VI. 45., of T. Maugèi [repeated here (fig. 40.c, d)] has

the lateral furrow 40

passing under the side of the caudal shell [erroneously: see in p.229.). In the animal here, the furrow, as is shown in my figure (39. b, c), commences near

the top or anterior edge of the shell, by a double nearly united line, which diverges in a sort of erratic direction on both sides of the animal, dividing the sides into unequal portions, until it terminates near the head. This line is better seen when the animal is extended, as are also the granulations or shagreen which are spread over the skin. It will be observed that I have shown six, instead of four, tentacula Cour engraver has omitted the sixth]. The fact is, that the animal can, at its pleasure, expand and convert the corners of the lip into a subsidiary retractile pair, in place immediately beneath the anterior pair, to which they are equal in dimensions and similar in appearance. This fact may account for the difference of opinion which has obtained on the number of these organs.

The eggs are perfectly oval, hard, and opaque; when fresh, white and covered with a clear viscous juice; when older, they assume a deeper tinge, much like that of the egg of our

VOL. VII. - No. 39.

Q

game fowl, or that of the eggs of some fowls of the Bantam
breed. They are not elastic, but have, like the eggs of the
common fowl, a regular shell of lime, which effervesces
strongly in acids. These eggs, if taken from the ground,
and cleaned and brought into the warmer atmosphere of a
room, will, in a few minutes, burst with a loud crack, and
disperse their shell and contents to a considerable distance.
Whilst I have been writing these remarks, one of the Testa-
célli before me has, in the space of twenty minutes, laid two
eggs (fig. 39. d). I sketch the animal as it presented itself
while engaged in the operation, during which the head and
tentacula were drawn in, to the degree shown in c.
The mildness of the climate of Guernsey during the winter
is, doubtless, the cause of the Testacéllus being to be found at
this period of the year. I should, however, state that those
which I found in 1801 were, as in the cases remarked in VI.
43. and 45., usually in the neighbourhood of a green-house.
Guernsey, Jan. 18. 1833.

[Of Testacéllus sciitulum Sowerby, Mr.Thomas Blair, Stamford Hill (VI.43.), obligingly sent me, on March 21. 1834, a supply of specimens; nine living individuals, one dead one, and five eggs. These I carefully compared with the characteristics of the Guernsey Testacéllus, as noted in Mr. Lukis's description, and shown in his admirable drawing. I could not perceive any mentionable difference between them, except that in the Stamford Hill animals the lateral furrow was less obvious, though still perceptible, than Mr. Lukis's drawing represents it to be in the Guernsey ones. I placed one of the eggs close beside the fire: it exploded, just as Mr. Lukis's had done. Most, or each, of the slugs themselves, exhibited, as it were, three pairs of tentacula, but I think that the pair produced by the protrusion of the corners of the lip were scarcely so long as the pair above them.

On holding one or more of the slugs by the body, between iny finger and thumb, I felt and saw my flesh struck with some white organ projected from the mouth of the slug. This, and a recollection of the worm-eating (vermivorous) habits of this species, instigated me to capture a smallish earthworm, and place it against the mouth of first one slug, then another. One endeavoured to take it, and its first act in the effort was darting out the organ I have mentioned, affixing it to the worm, and drawing the worm into its mouth. The worm, by its writhing, twisted itself out again, and this more than once, during the (about six) times which I, in the

[ocr errors]
« ZurückWeiter »