Imágenes de páginas

of this worm, and an enumeration of its parts may well strike us with wonder and admiration. “If the plume of an adult,” says Sir John Dalyell, “ displays eighty branchiæ, with five hundred cilia on each side, here are no less than forty thousand organs endowed with voluntary, distinct, and independent action. So many other parts are alike privileged in their own peculiar motion without the participation of the rest, that it is no exaggeration to affirm that the will of this timid, lowly, defenceless creature is fulfilled through the control of fifty thousand living parts.” None of the Annelides, we are told by those who have studied the history of this interesting worm, is more richly endowed with the power of repairing wounds and losses. These branchial plumes, noticed above, may be thrown off and replaced with new ones, and a large portion of the body may be amputated, and ultimately completely restored. Nay, Sir J. Dalyell informs us that a small portion of the abdominal part of the body has grown to be a perfect individual, has reproduced segments of its own kind, thoracic segments of different character, and the head with all its gorgeous plumes. For a further account of this interesting Annelide see the account given by Sir J. Dalyell in his Powers of Creation.”

The Serpulæ are the last of this order of Annelides that we shall mention. These worms are of an elongated form, and composed of numerous segments. The head is crowned with plumose branchiæ in two erect fan-shaped tufts, and they possess two tentacles, one of which is sharp-pointed, and the other dilated at the extremity into an operculum. The feet are setigerous ; but the thoracic and abdominal bristles are reversed in position. The operculum presents good characters for distinguishing the species.

We have figured one species which is common on some parts of our coasts, the Serpula vermicularis, or contortuplicata (Plate IV., Fig. 6). It inhabits a round shelly tube, tapered regularly backwards, and marked on its dorsal surface with a more or less distinct keel. It is about three inches long, and its aperture is circular, with an even or somewhat everted rim. Many tubes are usually found growing together, adhering to some old shell, a bit of broken pottery, or a stone, all much intertwined, and mutually adherent, so that it is practically hopeless, as Mr. Gosse says, to attempt to isolate one.

Sometimes, however, the tube in which this worm dwells is solitary, and may be found creeping along some old shell, and occasionally we find it only partially adherent, and the anterior portion standing erect. This tube is much longer than its inhabitant. Its length, says Mr. Gosse, is by no means commen

surate with the length of its house, of which, indeed, it inhabits only the last made portion, leaving behind a roomy space into which to retire in case of need. It is only about an inch in length, and there is a well marked difference between the thorax and abdominal portion. The former carries on each side prominent tubercles, in place of feet, which are vigorously protrusile, and within which bundles of strong bristles are thrust to and fro. On the upper part of each foot, extending half across the back, is a row of microscopic hooks, wielded by long thread-like tendons, which are fixed on mechanical principles to the attached end of each hook. By the aid of these the serpulæ very cleverly withdraw themselves with lightning-like rapidity on alarm. “ These organs are formed on the model of a hedger's bill-hook, only that the edge is cut into long teeth. Carefully counting them, I have found that each serpula carries about 1900 such hooks on its corselet, and that each of these being cut into seven teeth, there are between 13,000 and 14,000 teeth employed in catching the lining membrane of the tube, and in drawing the animal back.” The feet on the hinder portion of the body are, according to Mr. Williams, modified in structure, with express reference to the duties of mopping, sweeping, scraping, and wiping the inferior closed end of the habitation. The branchiæ, or breathing organs are much modified, both in position and form. “ They consist of most elegant comb-like filaments, richly coloured, arranged in two rows around the front extremity, one row on each side of the mouth. They are graduated in length, and are so affixed, that, where the rows meet behind, they can be thrown in, so that a vertical view of the circular coronet shows a great sinus in it. These brilliant gill-tufts form the most attractive feature in these elegant worms, and are individually most exquisite examples of mechanical contrivance. Examined under a low microscopic power, they present a most charming spectacle. Each filament consists of a pellucid cartilaginous stem, from one side of which springs a double series of secondary filaments, like the teeth of a comb. Within both stem and filaments the red blood may be seen with beautiful distinctness, driven along the artery and back by the vein (which are placed close side by side) in ceaseless course, contributing a very striking spectacle. The exterior of these organs is set with strong cilia, so arranged that the water current is vigorously driven upward along one side of the filament, and downward along the other.This current brings the food destined for the nutrition of the animal into the funnel formed by the branchiæ, as mentioned in the case of Terebella, at the bottom of which is the mouth, along

with a quantity of water, which, again, is expelled by means of a ciliated lining of the hinder parts, in a strong current, impinging against the closed end of the tube, and which carries with it all extraneous or fecal matters. " What a beautiful and effective contrivance,” says Gosse, “is this for constantly keeping in a state of the most unsullied cleanness the interior of the house ! It reminds one of the fabled Hercules cleansing the Augean stables by driving the river Peneus through it.” In our notice of the genus, we have mentioned that the animals are provided with two organs like the antennæ of insects, one of which is acute at the point, the other dilated in the form of an operculum. In this species it is broad and trumpet-shaped, somewhat concave at the extremity, and delicately marked with radiating grooves. “This organ is usually painted with the same brilliant colours as the gill-tufts, and, by its length, size, and form, makes a very conspicuous figure in this charming . serpula. Its length is such, that when the gill filaments are rolled up and withdrawn, the conical club enters after all, and is found accurately to fit the trumpet-like orifice of the tube, just as a cork fits tightly into the mouth of a bottle.”

Fig. 1.-Aphrodita hystrix-natural size.
Fig. 2.-Amphinome didymo-branchiata-natural size.
Fig. 3.—Nereis cærulea—natural size.
Fig. 4.-Phyllodoce Paretti.-natural size.

Fig. 1.-Cirratulus tentaculatus-natural size.
Fig. 2.—A branchial tuft of Arenicola—magnified.
Fig. 3.--Sabclla pericillus—Head portion, natural size.
Figs. 4 & 5.-Uncini, or hooked setæ of tubicolous An-

nelides-much magnified.
Fig. 6.-Serpula vermicularis-natural size.
Fig. 7.-Hirudo medicinalis, var.-natural size.

* Plate III. was given with the April number, opposite page 161.




Superintendent of Education in the Colony. In all tropical and semi-tropical lands insect life is a wonder and a power. In such situations it very commonly rivals vegetation itself in the luxuriant reply which it makes to the appeal of almost constant sunshine, and in the busy energy and endless diversity with which it presents itself in every direction, and at every turn.

In this particular the South African colony of Natal, lying between the 28th and 31st parallels of south latitude, and but a hundred miles outside the boundary of the southern tropic, is no exception to the rule. The insects of Natal are both busy and important members of the young colonial community, and never-failing objects of interest to those who there care to watch them in their manifold operations. It must also be added that in this especial district of Insectdom, they prove themselves by no means the bad neighbours they are reputed to be in somewhat analogous situations in other parts of the world. They are loud, and active, and numerous, and strong, but, on the whole, behave themselves with courtesy and forbearance towards the two-footed intruder who has of late years trespassed within their six-footed dominions. Some passing illustrations may be given in support of this certificate of character before Natal insect life is looked at from a different point of view.

In the first place those notorious burglars, the white ants, are abundant in various parts of the colony. Their hillocks lie in the path of the horseman in all directions as he rides across the open, fenceless country. But, in the eyes of colonial experience, these active and stealthy marauders are certainly not such ruinous and destructive pests as they are reputed to be on the almost unanimous testimony of insect books. They were originally in force on the spot were the capital of the colony, the city of Pietermaritzburg now stands; and at certain seasons of the year the ground may still be seen in the early morning strewn with the stripped wings of the swarms of the male insect. The floors of the original court house of the city have twice been replaced, in consequence of the old ones having been consumed by these little depredators, and minute orifices in the plastered walls of the public hospital, standing at the

entrance of the town, show that the white ant has been at work among the rafters above. But these things are occasionally made the subject of a passing remark. Some one says to his neighbour, “Some day the flooring of such a place here, or the rafters of such a place there, will have to be renewed, for the white ants have been among them.” The thing is taken as a matter of course, and that is all that is thought or said upon the subject. In the open country, settlers commonly make some little trifling repair to their houses, replacing posts or beams, and renewing plaster, because the white ants have been busy with the structure; and, in new buildings, creosote and tar are now getting to be more generally used in connection with the foundations. But, beyond this, it is rarely thought worth while to take the trouble to enter upon either hostilities or precautions. The author of this paper has thrice encountered the nest of this insect in his own garden, in what would generally be deemed objectionable proximity to walls and book-cases. But this is all he has ever personally known of his insidious neighbours; the nests being eradicated, and the queens bottled up, as a matter of course, when stumbled upon. In gardens the nests are commonly made in the earth and sod fences which are most generally in use, and which are very convenient as saving the busy insects some considerable amount of constructive labour. In the open country the hillocks which have to be reared, where there are no fences ready to supply their place, are about eighteen inches or two feet high. They are simple cones, with truncated and rounded tops, well hardened and baked by the strong sunshine. But the symmetry of their form is very constantly marred by the claws of the ant bearthe larger ant-eater of the zoologist—the cone being torn down on one side, and the debris of the structure, the disintegrated ant mortar, or “ant-heap," as it is technically termed, being scattered upon the ground. The ant bear is very plentiful, and the large, open mouths of its capacious and deep burrows are continually encountered in all directions, often most unwelcomely and unpleasantly, by the feet of horsemen's steeds, in the concealment of thick grass. But the animal itself is never seen, unless it is dug out from its retreat, and it requires some skill and practised ability to accomplish this feat, as he is a better and more speedy excavator than the general run of his assailants, and will make his way more quickly into the earth than any small number of picks and spades can follow him. His own operations among the ant hills are always carried on under the cover of darkness. He is very wary and stealthy in his habitual work, and exceedingly quick in his movements. The

[merged small][ocr errors]
« AnteriorContinuar »