466 POLYZOA. 



pharynx, are swallowed by a vigorous contraction of its parietes, and 

 carried rapidly down the oesophagus and through the cardia to the giz- 

 zard, that expands to receive them. Here they are submitted to a sort 

 of crushing operation, the parietes of the organ contracting firmly upon 

 them, and the two dark bodies being brought into opposition. Their 

 residence, however, in this cavity is only momentary, and they are 

 immediately propelled into the true stomach below, where they become 

 mixed up with its contents, which, during digestion, are always of a 

 dark, rich brown colour, being tinged with the secretion of its parietal 

 follicles. 



(1203.) The food appears to be retained for a considerable time in 

 the stomach, and may be frequently seen to be regurgitated into the 

 gizzard, whence, after having been again submitted to its operations, it 

 is returned to the stomach. Here it is rolled about by the contraction 

 of its parietes, and at its upper part is frequently submitted to a rotating 

 motion. This rotation of particles is chiefly near the pyloric orifice ; 

 and a mass may be occasionally seen projecting through the pylorus 

 into the intestine, and rotating rapidly in the direction of the axis of 

 the orifice. In an animal having a similar form of pylorus to this, but 

 in which the parts were more transparent, the cilia, by which this 

 rotation is eifected, were distinctly perceptible, surrounding the orifice. 



(1204.) The granular matter, after rotating for some time at the 

 pylorus (a provision for preventing its too rapid escape from the 

 stomach), passes into the intestine, where it accumulates in little pel- 

 lets, that are rapidly pushed, by the contraction of the intestine, towards 

 the anal orifice, through which they are expelled from the body. 



(1205.) The tube or cell inhabited by this Polyzoon is of exquisite 

 structure, and the mechanism concerned in the protrusion and retraction 

 of the animal of great simplicity and beauty. 



(1206.) The inferior two-thirds of the cell in the species under con- 

 sideration is hard and corneous, but perfectly transparent : the upper 

 third, on the contrary, is flexible, and so constructed as to form a very 

 complete operculum whereby the entrance is guarded. The flexible 

 part consists of two portions, the lower half being a simple continuation 

 of the rest of the cell, while the upper is composed of a circle of delicate 

 bristle- shaped processes or setae, which are arranged parallel to each 

 other around the mouth of the cell, and are prevented from separating 

 beyond a certain distance by a membrane of excessive tenuity that 

 connects them ; this membrane is evidently analogous to the infundi- 

 bular termination of the cells of polyps already described. 



(1207.) When the Polyzoon retires into its abode, the setae and soft 

 termination of the cell are gradually folded inwards, in the manner 

 exhibited in the annexed figures (fig. 239) representing the various 

 stages of the process. The oesophagus, surmounted by its tentacula, 

 descends first, whilst the integument of the upper part of the body 



