86 



those of the two proceeding orders, are, according to Farre 9 

 tubular with terminal apertures. 



The mouth, which is powerfully muscular, is situated in the 

 centre of the oral disc, and opens into along, large, tubular 

 canal which terminates either in a gizzard or the stomach. 

 This canal, which may be called an oesophagus, is powerfully 

 muscular and very easily excited into action. When a polype 

 has succeeded in capturing its food, it is conveyed into this 

 oesophagus, which instantly contracts on it, and by a series 

 of graduated contractions and relaxations forces it onwards 

 under great pressure, to the gizzard or stomach. It is 

 marked in different parts of its length, especially in its 

 superior portion, by numerous closely arranged circular spots ; 

 at each extremity it seems more opaque than at any other 

 part, as if its two openings were guarded by circular muscles; 

 which is probably the case. In some species this canal opens 

 into the stomach ; but in others it terminates in a powerful 

 organ which has been called a gizzard. This gizzard, from 

 its inequalities of light and shade, appears to be of unequal 

 thickness; but there are always two dark spots, or circum- 

 scribed bodies, placed opposite each other. Sometimes the 

 circumference of each of these spots is plain; at others marked 

 with radiating lines, apparently formed of folds. After nu- 

 merous examinations it seems to me most probable that 

 muscular fibres radiate from these points over the whole 

 organ, and consequently when they act, these points are 

 brought into close approximation, and in their motions grind 

 the food down to a pulp fitted for digestion; and such a dis- 

 tribution of fibres would also produce the folds occasionally 

 seen. This organ opens inferiorly into the stomach, which 

 is a long, large muscular sac extending to the base of the cell. 

 It is semi-opaque, and very irritable; its surface is marked 

 with minute irregular spots, which appear to be gastric folli- 

 cles for the secretion of a coloured fluid for digestion. It is 

 an organ, however which is liable to considerable variations 

 in size, depending probably on the quantity of food in it at 

 the time. It is fixed in its proper situation by thin fiat 

 muscles attached to different parts of its surface. This organ 

 seems to perform the functions of the stomach and small 

 intestines in higher animals ; for the food remains in it 

 longer than in any other organ, is digested there, and 

 afterwards passes with great rapidity through the remaining 

 tube. From the upper edge of the stomach arises another 

 canal which, ascends between the sides of the polype and the 

 oesophagus, and terminates in a small orifice near the rim 

 of the tentacula. In some species the gizzard is absent,, 

 in which case the first tube, or oesophagus opens into the 

 stomach. 



