XVI INTRODUCTION. 



touched with instruments without much effort at con- 

 traction. 



The gular tube is remarkably corrugated longitudinally, 

 the folds being so full, that a transverse section would 

 present a series of figures 8. In the present state of con- 

 traction there were horizontal corrugations also. At a 

 short distance below the mouth the stomach ends abruptly, 

 the edge, thin and delicate, hanging freely like a much 

 folded curtain into the cavity. At each angle of this 

 flattened sac the gonidial groove was conspicuous from top 

 to bottom, inclosed by two slender columns of the firm 

 cartilage-like muscle. 



The diameter of the digestive tube is, when at rest, not 

 greater than that of the mouth ; indeed, the walls are in 

 contact; nor, so far as my observation extends, are they 

 ever separated except for the reception of food. 



It has been customary to represent the stomach as a sac 

 pierced at the bottom " by one or more valvular openings 

 which communicate with the cavity of the body."* But 

 the case is as I have stated it : the free folded membrane 

 hangs perpendicularly ; nor is there any thickening of the 

 edge, nor any structure which at all resembles a sphincter. 

 In tall specimens, I have observed, through the semi- 

 transparent integuments, food pass into the stomach, and 

 have marked that the morsel is invariably retained, never 

 passing through to the general cavity ; but I am persuaded 

 that this is effected by the common contractility of the 

 walls, and not by a sphincter. 



"When morsels of food, such as fragments of butchers' 

 meat, are swallowed by Anemones, they are retained for 

 some hours, and then vomited ; and because little change 

 has passed upon the solid parts it has been rashly concluded 

 that no process of digestion takes place in these animals. 

 On this foolish hypothesis it is difficult to see why food 

 should be swallowed at all, or what need the animal has of 

 mouth or stomach. Their ordinary food, however, is not 

 mammalian muscle, but the far softer and more fluid flesh 

 of Crustacea, Mollusca, and Annelida. Nothing is more 

 common than to find large specimens of A. mesembryan- 

 ihemum or T. crassicornis discharge, soon after their capture, 



• Siebold's Comp. Anat. § 37. " The stomach with its circular aperture 

 at the oase " (Teale). Johnston, indeed, denies it any aperture at all : — 

 * There is no — other visible exit from the stomach than the mouth." 



