530 CILIOBRACHIATE POLYPES; BOWERBANKIA. 



The protrusion of the body takes place by a contrary series 

 of processes. The bundle of setce first makes its appearance 

 out of the apex of the cell, and is followed by the flexible portion 

 on which it is set. The tentacula next pass up between the setae 

 and thrust them asunder ; while the integument is seen gradually 

 rolling onwards from around the tentacula. These latter con- 

 tinue to emerge, and the integument to be inverted from around 

 them, until the base of the tentacula has risen above the top of 

 the expanded setae ; when the act of protrusion is completed, the 

 tentacula separate and expand, and the cilia commence vibrating. 

 These actions are generally performed with an extraordinary 

 rapidity ; and it is only when they are executed with unusual 

 slowness, that the several movements concerned in them can be 

 distinguished. 



1102. Upon reviewing the complex organisation of this 

 minute Polype, it must be admitted that its mechanical functions 

 are executed with a degree of perfection, which cannot but excite 

 our surprise and admiration ; and not less interesting is it to 

 observe the other vital operations exhibited by it, which the 

 transparency of the whole structure enables us to watch with no 

 interruption. The little animal, when in full vigour, is seen 

 projecting from its cell with the arms extended and the cilia in 

 active operation ; the upper part of the body being frequently 

 turned from side to side over the edge of the cell, the extremity 

 of which, from its peculiar flexibility, moves along with it. 

 The action of the cilia forms a kind of whirlpool, by which the 

 particles contained in the surrounding water are carried into the 

 funnel-like pharynx. By the contraction of its walls, they are 

 carried rapidly down the oesophagus into the gizzard, which 

 expands to receive them. Here they are submitted to a sort of 

 crushing operation ; the movement of its walls very much resem- 

 bling that, which is seen in the dental apparatus of the Wheel- 

 Animalcules ( 857). Their residence in this cavity, however, 

 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 by the secretion of the biliary follicles 



