74 The Animal Mind 



tacle tip, where they drop off. When a bit of crab meat, 

 or some meat juice, is dropped on a tentacle, the latter 

 contracts and curls over with the tip directed toward the 

 mouth. The ciliary movement continuing in its usual di- 

 rection now of course carries the food toward the mouth. 

 Applying food to the lips on either side of the mouth causes 

 a different response. The ciHa on these lips ordinarily 

 wave outwards ; when food is brought in contact with 

 them their motion is reversed, and the food is thus passed 

 into the mouth. In Metridium, then, there is no specific 

 rejecting reaction for inedible substances (533). 



Various instances of the effect of physiological condition 

 upon response to food stimulation in sea-anemones have 

 been noted. Adamsia loses the power to discriminate 

 between edible and inedible substances when very hun- 

 gry (521). Sagartia davisi will also swallow inedible sub- 

 stances if hungry enough (715). Stoiachactis helianthus 

 will give either a positive or a negative reaction to food 

 according to its condition of hunger or satiety (374). The 

 reaction of Metridium to food may vary decidedly with the 

 degree of hunger (3), although it will continue taking food 

 as long as the process is mechanically possible (378). Fa- 

 tigue has also been shown to affect the food responses of 

 Metridium and other sea-anemones; specimens that have 

 been fed meat and filter paper alternately will after a time 

 'refuse to take filter paper (374, 521, 533). This behavior 

 was thought by Nagel to indicate that the animal had dis- 

 covered the deception practised upon it ; but according to 

 Gee (256) the real cause is increased secretion of mucus, 

 which lowers the responsiveness of the animal. This 

 effect would naturally be felt first in response to weak 

 stimuli. 

 /^As regards the localization of the sensitive elements, 



