278 Mr. E. W. H. Holdsworth on Digestive Power in the Actinise. 



be entirely swallowed : on its disengagement from the animal, 

 that portion of it which had passed the mouth will be seen 

 thickly covered with the secretion. One frequent source of 

 error in studying the digestive powers of the Actinice arises from 

 the belief that all the food these animals swallow must necessa- 

 rily undergo digestion, whatever the nature of that process may 

 be ; but this is far from being the case. Healthy polypes will 

 rarely refuse anything that comes within their reach ; and in 

 most cases it is only after the object has passed through the 

 stomach, that the animal finds out whether it is hungry, or if it 

 has swallowed suitable food. In my own tank, a specific-gravity 

 bubble has been gulped down by almost every specimen large 

 enough to accomplish the feat, and by some of them more than 

 once ; but of course it is always ejected unaltered : in the same 

 manner, proper food has been taken in and returned after a 

 short time only, not from its being indigestible, but because 

 . the animal was not hungry. In our own case, over-eating 

 is generally followed by indigestion; but the polype has a 

 very ready mode of preventing such an unpleasant result. 

 When its appetite is appeased, or its powers of digestion ex- 

 hausted, it simply throws up what remains of the food; and 

 this circumstance will explain the different states of the ejected 

 meat, and the reason why large pieces are so often cast forth 

 with little apparent alteration, A case has recently presented 

 itself which shows this to be a reasonable inference. Two 

 specimens of Cerianthus, which had been living side by side for 

 a couple of years in a tall glass jar, were fed with small and 

 equal portions of beef, and after a time each animal threw up 

 the remains of its dinner. In one case, where the polype had 

 been fasting for a week, the food was returned after twelve 

 hours very little altered in shape; muscular striae were percep- 

 tible under the microscope, and the general appearance of the 

 meat indicated its having undergone maceration, but not com- 

 pression. In the other example the refuse was cast up, after an 

 interval of sixteen hours, in very small particles without any 

 trace of muscular structure, and so far disintegrated as to render 

 their removal from the water a matter of some difiiculty. This 

 polype had not been fed for six weeks ; and the different results 

 from the two animals may be fairly accounted for by the un- 

 equal intervals between their last two meals. In the true Ac- 

 tinice there is the same variation in the extent to which digestion 

 is carried as in the instances just cited, and in a great measure 

 it will bear the same explanation : we also find it partly depend- 

 ing on the digestible nature of the food swallowed. In the 

 account of Mr. II. Q. Couch's experiments, quoted in ^ Seaside 

 Studies,' p. 217, great stress is laid on the fact that the delicate 



