BEHAVIOR OF METRIDIUM. 37 



taking of food by Mctriduim. Muscular movements of the ten- 

 tacles, disk, and oesophagus also plays a part, but a less impor- 

 tant one than in the anemones studied by Jennings (1905). The 

 tentacles bearing bits of food are bent toward the mouth, and 

 the cilia of the tentacular surface carry the food toward the mouth 

 opening. The cilia of the oesophagus are usually beating out- 

 ward, but when food enters the mouth the stroke of the cilia of 

 the part in contact with the food becomes reversed, so that the 

 food body is conveyed inward (see Parker, 1896, 1905). I have 

 found that the reversal of the cesophageal cilia is frequently 

 caused in JMctridiuui by indifferent solids, such as filter paper, so 

 that such bodies are ingested. 1 There is much variation in regard 

 to this matter, some individuals take filter paper readily, others 

 slowly and only at times, others not at all. As we shall see 

 later, this depends largely on the degree of hunger. 



We will now take up experimentally the various possibilities 

 of modification above distinguished. In studying these matters, 

 it is most important that specimens which are fresh and in good 

 condition should be used, otherwise clear results will not be 



7 



obtained. 



I. Hunger. Conditions of hunger and satiety affect the food 

 reactions of Metridinin in a most decided way. When the animal 

 is very hungry (and in good condition otherwise), the column is 

 extended, becoming long and slender, while the disk is widely 

 spread, and the tentacles extend a considerable distance beyond 

 its edge. If the animal remains contracted, it can often be in- 

 duced to extend by placing a piece of clam meat or some meat 

 juice on the infolded disk. Two or three applications of food 

 will often cause the most obstinately contracted specimens to ex- 

 pand beautifully. If now a piece of mussel of considerable size 

 (having an area equal to the cross section of the column, with a 

 thickness of three or four millimeters) is brought near the edge 

 of the disk, so as to come in contact with the tips of two or three 

 tentacles, a decided reaction is produced. The tentacle tips ad- 

 here to the meat, and the tentacles and adjacent parts of the disk 

 contract quickly, so that the piece of meat is drawn inward. It 



1 This was possibly due, as Parker (1905, 1905*7 } has set forth, to the paper's 

 having been touched by the fingers ; this matter was not tested. 



