213 



The sensory reactions of the common sea anemones have been our 

 chief study, the enquiry being made in part for the purpose of arbitrating 

 between the conflicting views of Nagel and Loeb, and, in part, to pic- 

 ture as far as possible the manifestations which make up the life of ane- 

 mones. We shall discuss the reactions to mechanical stimuli, to chemical 

 stimuli, and to the stimulus of light, adding notes on the question of 

 persistence of impressions received, on inferences as to the nervous system 

 of the group, and on various details of the life of anemones which have 

 come under observation. 



II. Romanes (1883) says that if an anemone is near the surface in a 

 tank and a jet of water is playing on the surface, the animal is soon 

 surrounded by a turmoil of bubbles. Soon it will none the less expand 

 the tentacles just as in calm water. If now an expanded tentacle is 

 gently touched by a solid body several others close round it, i. e. the 

 tentacles show differential reaction to the stimuli supplied by the 

 turmoil of bubbles, and those supplied by contact with a solid bod}'. 

 We have found that Actinia ., Tealia, and Anthea take practically 

 no notice of such a turmoil of bubbles while Sagartia sphyrodeta, 

 and S. troglodytes react by retracting more or less and the same 

 result is obtained with Aiptasia Coiichii and Bunodes gemmacea. Ten- 

 tacles show very little reaction, if any, to chance contact with a pebble 

 that is being moved in the aquarium, but react markedly to contact with 

 a finger. The edge of the base is probably the most sensitive region for 

 mechanical stimuli, the animal closing very quickly if this is touched. 

 The surface of the column is sensitive throughout its length but more 

 so towards the edge of the base. The disk and mouth are less sensitive 

 to mechanical stimuli, in Tealia this dullness is peculiarly marked. The 

 tentacles have naturally developed a high degree of sensitiveness to 

 mechanical stimuli and, as we have just seen, a fair amount of differential 

 reaction to them. 



III. Pollock and Romanes (1882) believed that anemones were 

 capable of distinguishing food when it was placed near them, but could 

 not tell the direction unless it was exceedingly close. Nagel (1892 — 1894) 

 found that the tentacles will take flesh but refuse inedible matter such 

 as filter paper. They will, however, he says, take the latter when soaked 

 in meat extract, and meat etc. placed near the mouth induces a reaction 

 only when the juices have diffused out to the tentacles. He believed that 

 Actinia^ Adumsia^ Aiptasia, Anthea, and Ceriantlms have a sense of taste 

 in the tentacles which he describes as Wechselsinnesorgane, sense organs 

 responding to different classes of stimuli. 



Loeb (1895j cut the tentacular crown away and found that the 

 remaining stump took up food but speedily rejected paper or sand and 



