ravings represent two species of the latter kind, which are, on
account of the peculiar appearance of their skeleton, called glass
sponges.

Fig. 1 represents the "sprinkling pot sponge," _Eucleptella
aspergillum_. It is generally found in very deep water throughout the
Pacific. Specimens were found over fifty years ago, but, as they had
to be brought up from depths between 500 and 800 fathoms, they
remained very scarce and sold at fabulous prices.

[Illustration: Fig. 1.--SPRINKLING POT SPONGE.--(_Eucleptella
aspergillum_.)]

The skeleton is formed by small crystals and long threads of vitreous
silica, cemented together, during life, by protoplasm. They are
arranged in longitudinal and annular bands so as to form a long curved
cylinder, about nine to twelve inches long, the walls of which are
about one inch in thickness. The threads and bands are interwoven with
the greatest regularity, and when the skeleton is freed from the
adhering organic matter, it looks extremely beautiful.

The mode in which the intersecting bunches of crystals are connected
is shown in Fig. 2. The upper end of the cylinder is closed by a
perforated cover, which probably has given rise to the name of the
sponge. The upper portion of the cylinder is surrounded by a few
irregular, annular masses of organic tissue, which adheres loosely
only to the skeleton. The lower end is formed by a bunch of long
threads, rooting firmly in the ground.

[Illustration: Fig. 2.--SPONGE CRYSTALS MAGNIFIED.]

Up to about ten years ago the price of specimens of this sponge was
very high. At that time, however, a colony of Eucleptellas was found
near the cities of Cebu and Manila, in the East Indies, in a depth not
exceeding 100 fathoms, and since they have appeared in larger
quantities in the market. It is remarkable that, contrary to their
habits, these organisms have immigrated into regions to which they
were totally unaccustomed. Yet it must be regarded as a greater
curiosity that they have been accompanied to their new abode by a few
animals living in equally deep water and never met with before at
depths less than three or four hundred fathoms. Among these animals is
a _Phormosoma_ (water hedgehog), noted for its long spines.

Glass sponges are not confined to tropical regions. They are met with
in latitudes as high as the Faeroee Islands, where the beautiful
_Holtenia Carpentaria_ abounds. It is represented in Fig. 3. Its
cup-shaped skeleton is similar