372 F. W. GAMDLE AND FREDERICK KEEBLE. 



liinder ends disintegrate whilst attached to, or in the neigh- 

 bourhood of, the capsules, and attract swarms of bacteria 

 and ciliate Infusoria. Thus at the time of hatching C en- 

 voi uta finds itself surrounded by an inexhaustible store 

 of food (see PI. 30, fig. 3). If we picture the vast numbers 

 of egg-capsules that are laid by these extensive colonies ; if 

 we add to the capsular fauna and flora the free living forms 

 of life that swarm in the sand; and if, further, we add the 

 organisms that doubtless infest the capsules of these free 

 living forms; we shall have some idea of the illimitable 

 supplies of food that these stretches of fertile sand afford 

 to their inhabitants. 



We now describe the apparatus by the aid of which 

 Convoluta ingests, digests, and circulates its food. The 

 larva — that is, the animal just after hatching — possesses a 

 central nucleated tissue which forms a sponge-work, the 

 meshes being composed of a firmer substance, with nuclei at 

 intervals, and containing a more fluid plasm. This tissue is 

 strongly developed in the hinder half of the body, and forms 

 a conspicuous protrusion on the ventral surface. It appears 

 to communicate with the exterior by a mouth placed almost 

 in the centre of the under surface. Two concentric delicate 

 markings probably represent the mouth, but the appearances 

 are such as do not justify a definite statement. Such as they 

 are, they point to a sphincter which is kept closed, and is 

 presumably only relaxed at the moment of ingestion or 

 ejection of food or of remains of food. In later stages the 

 mouth and pharynx are easily recognisable at this point. 



In the central syncytium there are, even at the time of 

 hatching, one or more nucleated delimited masses of cytoplasm. 

 At an early stage two of them are present just above the 

 mouth. These are the wandering cells, which ingest the 

 food and then move backwards to the thicker, hinder part of 

 the body. In larval Convoluta they may be seen in that 

 position enclosing alg;c or other nutritive substances. 

 Frequently they fuse to form a multinucleate mass in this 

 hinder region. Such a structure is constantly to be seen in 



