Plumatella repens(*) (Fig. 22) forms brown branching colonies, wholly or partly adherent to the surface of leaves of water plants, old wood, etc. The individual cells are club-shaped, and about a quarter of an inch long, each cell being attached to the upper back part of the cell below; the statoblasts (Fig 21, B) are simple oval bodies with a zone of air cells.
Plumatella (Alcyonella) fungosa forms thick masses, composed of closely packed vertical tubes. A small specimen(*) surrounding a stick from Hampstead Ponds is exhibited.
Lophopus crystallinus(*) occurs in the form of translucent gelatinous blobs, often attached to the slender stems of duck-weed. The statoblasts (Fig. 21, C) are elliptical and pointed at each end. The polypides are comparatively large, and can be easily observed through the transparent surface. When its delicate plumes are fully expanded, Lophopus forms a beautiful object.
Cristatella mucedo(*) (Fig. 23) occurs in the form of greenish translucent oval or worm-like colonies with the polypides on the convex upper surface. The animal slowly creeps about on its flattened under surface.
Fig. 23.
Cristatella mucedo, creeping over a stem of water-weed; × 6. (After Allman.)
a, polypides with horseshoe-shaped crown of tentacles; b, statoblasts seen through the tissues; c, muscular sole by means of which the animal creeps; d, stem of water-weed.
Freshwater Polyzoa usually prefer dark places, but Cristatella creeps along on the stones and pebbles in clear water, and in the sunlight. The polypides form three or more concentric rows on the upper surface. The statoblasts (Fig. 21, D) are circular, provided with a zone of air cells, and with hooked spines, the total diameter being about ¹⁄₃₀ of an inch.
Sub-class II.—Entoprocta.
Table Case A, upright part.
In this small group, both orifices of the alimentary canal open within the circle of tentacles, and there is no tentacular sheath.