CHAPTER IV.
MOSS-ANIMALS.
A little group of animals whose relationship with the sub-divisions previously and hereafter described cannot be very definitely determined is that of the Moss-animals, sometimes designated Corallines, or Lace-corals. All its members are of exceedingly minute size, and if living separately would be scarcely discernible to the unaided vision. They are, however, in the habit of forming stocks, or colonies, after the manner of corals, by a process of continual budding, and in this way build up social aggregations which may be of considerable dimensions. The majority are marine, and largely in evidence on almost every seashore in the form of the so-called Sea-mats, consisting of masses of minute, light brown, horny cells, which take the form of seaweeds, or are spread in thin, lace-like encrustations upon the surfaces of shells, stones, and the larger seaweeds. The living inhabitants of these cells are as transparent as glass, their most characteristic feature being the elegant shuttle-cock-shaped crown of tentacles which is thrust out or withdrawn at will from the aperture of each tiny tenement. The assistance of the microscope is requisite for the apprehension of these details, as also of the somewhat complex alimentary and other organs enclosed within the component cells.
Photo by W. Saville-Kent>, F.Z.S.] [Milford-on-Sea.
MOSS-ANIMALS.
These coral-like masses are composed of many thousand closely united dwelling-cells of microscopic dimensions.
A comparatively small number of these moss-animals are inhabitants of fresh-water, forming brown tubular aggregations on the under side of the leaves of water-lilies or other submerged objects. It is interesting to observe that the tentacular crown in almost all these fresh-water species is horseshoe-shaped, instead of like a shuttle-cock, as in the marine forms. One very notable fresh-water species is remarkable for the circumstance that in place of horny tubes the component individuals secrete a common transparent gelatinous matrix, which is provided with a creeping-base, wherewith the colony-stock is enabled to travel over the surfaces of the water-plants among which it lives, or up the glass sides of an aquarium. In some respects, and more especially their earlier developmental phases, the Moss-animals show affinities with the Lamp-shells, while the tentacular crown of the adult individual is closely imitated in certain worms.