i6o THE BIOLOGY OF THE SEA-SHORE 



is carried forward ; on reaching the centre of the foot 

 the contracted portion rises forming a wave that deepens 

 as it approaches the " anterior " end. On reaching the 

 '* anterior " edge the wave is retarded by the firmer attach- 

 ment of the edge, which releases locally, breaking the wave 

 into segments. A wave requires about a minute to traverse 

 the foot, and before it has disappeared another commences. 

 The same writer has also observed that anemones thrown 

 into an aquarium ejected acontia which caught hold of any 

 solid near them and contracted until some portion of the 

 foot touched the object and caught hold. In a later paper 

 McClendron (1908) has described a species of Cradactis 

 from the Tortugas which is able to crawl on its tentacles, 

 something after the manner of the fresh- water Hydra. The 

 tentacles employed are outside the ordinary ones, and are 

 branched structures resembling fronds of seaweed. They 

 are not used for conveying food to the mouth, but catch hold 

 of the substratum, from which, by considerable writhing, 

 the animal loosens the base and walks inverted on its tenta- 

 cles to a new place where it rights itself and settles down. 



Many anemones, while they remain for long periods in 

 the same spot, are capable of becoming distinctly active, at 

 least in the aquarium, and then cover considerable distances. 

 It is likely, however, that owing to the smooth bottom and 

 sides of the usual aquarium tank the distances covered are 

 greater than they would be on the shore — but this is merely 

 a matter of conjecture. Dr. Williamson, of the Scottish 

 Fishery Board, has observed the movements of a large 

 Metridium dianthiis in captivity, and has kindly supplied us 

 with tracings of the successive positions occupied by the 

 pedal disc. From these data the accompanying diagram has 

 been compiled. An interesting point in connection with 

 the movements of this specimen is that the periods of activity 

 would seem to be regularly punctuated with periods during 

 which the animal, though apparently unsettled, moves but 

 little. Or to look at the matter in another way, the larger 

 movements seem to be prefaced by a series of purely local 

 movements. 



