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inferior fine quality. Of the common sponges there is one in four of a first quality; the rest are of a second or common quality. Of the coarse, one-half are of a first quality, and the other half of a second quality. Thus, it will be seen that the fine, common, and coarse kinds of sponges may be divided into two qualities each.

The total imports of sponge into Great Britain in 1840 were 78,500 lbs. ; in 1841, 58,931 lbs. ; in 1855, 471,871 lbs. The quantity and value of the imports of sponge into the United Kingdom since have been as follows:

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The following is the French classification of commercial sponges —

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Lastly, the Bahamas and American sponges, which are divided into fine and common. Their tissue is loose, without elasticity, and hence they are easily torn.

They sell at a low price.

In the ten years ending 1860, the sale of sponge in

France was 2,000,000 kilogrammes, of the value of 10,600,000 francs (£424,000). The consumption is therefore about 150,000 kilogrammes per annum. There was imported into France in 1875 246,666 kilogrammes of

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Silicious sponges.

1. Euplectella aspergillum; 2. Holtenia carpenteria.

sponge, of which 93,324 kilogrammes were re-exported. In 1876 the imports reached 257,878 kilogrammes, and the exports were 89,600 kilogrammes.

Silicious Sponges.-Sponges are not confined to recent

seas, though the commercial ones are not known to have existed earlier, because the keratose matter furnishes hardly favourable conditions for petrifaction. In the oölite and chalk formations, sponges containing flinty spicules were very abundant; and in most of the earlier formations, large sponges containing calcareous spicules abounded. These very closely resemble corals, and have been mistaken for them by some of our best geologists. The spiculæ or needle-shaped particles, which are often microscopic in size, are not thrown in without order, but are arranged to support the skeleton. The horny sponges do not secrete or deposit spicules, but these are sometimes found within the skeleton in broken and disordered form, which show they were taken in from without.

The quantity of silica which constitutes the structure of sponges is remarkable. It generally occurs in the form of spiculæ in considerable quantities, imbedded in the substance or body of the sponge. One of the rarest and most beautiful of the silicious sponges is the Euplectella speciosa, found at the Philippine Islands. It is of cornucopia shape, and has a horny, skeleton-like network, composed of large silicious fibres running from the base to the head, surrounded by small fibres forming square, open meshes, resembling a net or basket work. It ranges in height from 6 to over 15 inches. At the lower extremity, or root, it averages about an inch in thickness, but its size gradually increases as it approaches the top, where often it is two inches wide. It is surmounted by a ridge about a quarter of an inch wide, and is closed at the larger extremity by a delicate open lacework of fibres, possessing no particular pattern. It is on this light and pretty structure that the fibrous, gelatinous substance rests, resembling in texture the common sponge, but in this instance disposed in an

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irregular, foliated pattern, over which the usual film of the sponge is laid during life.*

* Bryce M. Wright in "The American Naturalist."

At one time this sponge was so rare that specimens fetched enormous prices; now, by the progress of commerce, it has become more common, and specimens of great beauty may be had for a few shillings.

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