If calcareous sponges are to be preserved for future reference, they may be placed in diluted spirit, in which case the animal matter, as well as the mineral substance, will be preserved with but little alteration in the natural appearance and structure. A specimen which has been decalcified by means of acid, as above described, may also be preserved in the same manner; and small portions of this will serve for the microscopic study of the animal portion of the sponge. If the skeleton only is required, the sponge is simply allowed to dry, when the soft animal substance, on losing its contained water, will leave hardly any residue; or, better, allow the calcareous sponge to macerate in water for some days for the animal substance to decompose, and then, after a few minutes in running water, set it aside to dry. [Illustration: FIG. 68.--_Grantia compressa_] [Illustration: FIG. 69.--SPICULES OF _Grantia_, MAGNIFIED] Small portions of the skeleton, examined under the microscope, will show the nature of the calcareous spicules of which it is composed. These consist of minute needles and stars, the latter having generally either three or four rays. We give figures of three of the calcareous sponges of our shores, the first of which (_Grantia compressa_) resembles little oval, flattened bags, which hang pendulous from rocks and weeds, sometimes solitary, but often in clusters. The smaller openings are thickly scattered over the flat sides of the bag, and the larger ones, through which the water is expelled, around the margin. When the sponge is out of the water and inactive, the two opposite sides of the bag are practically in contact, but, when active, the cavity is filled with water by means of the whip-cells that line it, and the sides of the sponge are then more or less convex. [Illustration: FIG. 70.--_Sycon ciliatum_] The ciliated sycon (_Sycon ciliatum_), fig. 70, though of a very different appearance externally, is similar in structure to _Grantia_. It is also found in similar situations, and is not uncommon on many parts of the South Coast, from Weymouth westwards. The other example, _Leucosolenia botryoides_, shown in fig. 71, is a branching calcareous sponge, consisting of a number of tubes, all united to form one common cavity which is lined throughout with whip-cells. It is usually found attached to weeds. [Illustration: FIG. 71.--_Leucosolenia botryoides_, WITH PORTION MAGNIFIED]