_Gemmule_ A mass of cells packed with food-material, surrounded by at least one horny coat, capable of retaining vitality in unfavourable conditions and finally of giving origin to a new sponge. _Green corpuscles_ Minute green bodies found inside cells of sponges and other animals and representing a stage in the life-history of an alga (_Chlorella_). _Inhalent_ (or _afferent_) A tubular canal through which water canal passes from the exterior towards a ciliated chamber. _Megascleres_ The larger spicules that (in the Spongillidæ) form the basis of the skeleton of the sponge. _Microscleres_ Smaller spicules that lie free in the substance or the derma of the sponge, or are associated with the gemmule. _Monaxon_ (Of spicules) having a single main axis; (of sponges) possessing skeleton spicules of this type. _Osculum_ An aperture through which water is ejected from the sponge. _Oscular collar_ A ring-shaped membrane formed by an extension of the derma round an osculum. _Parenchyma_ The gelatinous part of the sponge. _Pavement layer_ Adherent gemmules arranged close together in a single layer at the base of a sponge. _Pneumatic coat_ A horny or chitinous layer on the surface of the gemmule containing air-spaces. If these spaces are of regular form and arrangement it is said to be _cellular_; if they are minute and irregular it is called _granular_. _Pore_ A minute hole through which water is taken into the sponge. _Pore-cell_ (_porocyte_) A cell pierced by a pore. _Radiating fibres_ Fibres in the skeleton of a sponge that are vertical or radiate from its centre. _Rotula_ A transverse disk borne by a microsclere. _Rotulate_ (subst. or adj.) Spicule bearing one or two transverse disks.