"During these operations the muddy materials are seen descending between the roots of the fans toward the trowels, while another organ, perhaps the mouth, is also occupied, it may be, in compounding the preparation with adhesive matter. As the bulk of the muddy mass diminishes, the activity of the worm abates; it is soon succeeded by repose, and then the tube is found to have received evident prolongation."

The gill-fans of this species are most lovely, forming a nearly complete funnel by their regularly radiating arrangement, and being colored gorgeously with scarlet, green, brown, and gold.

Then there is the FUNNEL AMPHITRITE (Amphitrite infundibulum), so called because the tentacles are so perfect in shape that, when fully spread, they form a circular funnel, in which scarcely the slightest break is perceptible. This funnel is rendered more complete by the curious fact that in each half of the fan the tentacles are united by a delicate and transparent web, reaching nearly to their tips. The prevailing color of these beautiful fans is purple, darkest toward the tips, and changing gradually to chestnut at the base.

This is not a plentiful species, and is mostly obtained by means of the dredge or drag, which tears up a portion of the ground, and brings with it the Funnel Amphitrite and its dwelling. This is of a tubular shape, and generally black, with a slight mixture of green. The color, however, is very variable, and depends much upon the age of the tube; for, when freshly made, it is nearly as transparent as that of the previous species. There are other species of Amphitrite, all of which are interesting, but which our diminished space will not admit.

SHOULD the reader happen to be an entomologist, he will readily call to mind the tiny cylindrical cases that are made by certain lepidopteran larvæ, belonging to the great family Tineidæ, and which are found so plentifully upon the leaves of oak, hazel, and other trees. If he should happen to be something of an aquarian naturalist, and fond of looking for marine curiosities, he may find attached to submarine plants certain little cylindrical cases which are wonderfully like those of the moths. They are very small indeed, scarcely thicker than the shaft of an ordinary pin, and measuring scarcely more than the eighth of an inch in length. Their color is pale brown, their surface is rough, and they are stuck upon the sea-weed in great confusion, without the least attempt at arrangement.

These are the habitations of a very small crustacean (Cerapus tubularis), properly called the CADDIS SHRIMP, because the tube which the creature makes is analogous to that which is formed. by the caddis larvæ. The animal which inhabits this case is a curious little being, very like the long-bodied, long-legged caprellæ, that are so plentiful among sea-weeds, and furnished with two pairs of long and stout antennæ, and two pairs of grasping feet. As the tube is too short to contain the entire animal, the long antennæ are always protruded, and occasionally the powerful grasping feet are also thrust out of the opening.

The antennæ are continually flung forward and retracted in a manner that reminds the observer of the movements of the acorn barnacle, each grasp being evidently made for the purpose of arresting any passing substance that may serve for food. This remarkable little crustacean is generally found upon the wellknown alga which produce the Carrageen, or Irish Moss (Chondrus crispus). It will not, however, be found upon those plants which can be plucked by hand, but resides in deeper water, so that the best method of procuring it is to go out in a boat, throw the drag overboard, and then examine the algae which are torn from their attachments.

CHAPTER XXI.

SOCIAL HABITATIONS.

SOCIAL MAMMALIA.

The BEAVER.-Its Form and aquatic Habits.-Need for Water, and Means used to procure it.Quadrupedal Engineering. -The Dam of the Beaver.-Erroneous ideas of the Dam.-How the Beaver cuts Timber.-The Beaver in the Zoological Gardens.-Theories respecting the Beaver's Dam.-How the Timber is fastened together.-Form of the Dam, and mode of its Enlargement.-Beaver-dams and Coral-reefs.-The House or Lodge of the Beaver.-Its Locality and Structure.Use of a subterranean Passage.-How Beavers are Hunted.-Curious Superstition.-"Les Paresseux."

WE now come to the SOCIAL HABITATIONS, and give precedence to those which are constructed by Mammalia.

Of the Social Mammalia, the BEAVER (Castor fiber) takes the first rank, and is the best possible type of that group. There are other social animals, such as the various marmots and others; but these creatures live independently of each other, and are only drawn together by the attraction of some favorable locality. The

Beavers, on the other hand, are not only social by dwelling near each other, but by joining in a work which is intended for the benefit of the community.

The form of the Beaver is sufficiently marked to indicate that it is a water-loving creature, and that it is a better swimmer than walker. The dense, close, woolly fur, defended by a coating of long hairs, the broad, paddle-like tail, and the well-webbed feet, are characteristics which are at once intelligible. Water, indeed, seems to be an absolute necessity for the Beaver, and it is of the utmost importance to the animal that the stream near which it lives should not grow dry. In order to avert such a misfortune, the Beaver is gifted with an instinct which teaches it how to keep the water always at or about the same level, or, at all events, to prevent it from sinking below the requisite level.

If any modern engineer were asked how to attain such an object, he would probably point to the nearest water-mill, and say that the problem had there been satisfactorily solved, a dam having been built across the stream so as to raise the water to the requisite height, and to allow the superfluous water to flow away. Now water is as needful for the Beaver as for the miller, and it is a very curious fact that, long before millers ever invented dams, or before men ever learned to grind corn, the Beaver knew how to make a dam and insure itself a constant supply of water.

That the Beaver does make a dam is a fact that has long been familiar, but how it sets to work is not so well known. Engravings representing the Beavers and their habitations are common enough, but they are generally untrustworthy, not having been drawn from the natural object, but from the imagination of the artist. In most cases the dam is represented as if it had been made after the fashion of our time and country, a number of stakes having been driven into the bed of the river, and smaller branches entwined among them. The projecting ends of the stakes are neatly squared off, and altogether the work looks exactly as if it had been executed by human hands. One artist seems to have copied from another, so that the error of one man has been widely perpetuated.

Now, in reality, the dam is made in a very different manner, and in order to comprehend the mode of its structure, we must watch the Beaver at work.

When the animal has fixed upon a tree which it believes to be suitable for its purpose, it begins by sitting upright, and with