2O8 HARRY BEAL TORREY. 



response, which spreads by the direct effect of the tension of 

 one muscle on those near it. 



The usual response of a tentacle stimulated indirectly in the 

 manner just described is a waving or arching toward the mouth, 

 with or without vigorous shortening of the whole tentacle. Occa- 

 sionally the response is quite opposite to this, the stimulation of 

 one tentacle producing an outward waving of neighboring tenta- 

 cles. The anomaly is only apparent, not real, for as a matter of 

 fact the muscles of the neighboring tentacles are not involved at 

 all in the latter case. The tentacles neither shorten nor bend. 

 They move outward stiffly, owing to a local contraction of 

 muscles in the oral disk or the capitulum. 



If the stimulus applied to a tentacle be sufficiently strong, all 

 of the tentacles may shorten simultaneously, may even be entirely 

 withdrawn into the body by the contraction of mesenterial muscles 

 and hidden by the contraction of the sphincter ; the column may 

 shorten also, and the foot disk may change its shape. All of 

 these movements seem to be induced by the direct passage of 

 the stimulus from muscle to muscle without the aid of nerve 

 tissue. 



The oral disk, between tentacles and mouth, is almost insensi- 

 ble to mechanical stimuli. 



Stimuli applied to the column produce the inward movement 

 of several or all tentacles, the outward movement of a few, or the 

 contraction of column and foot disk, according to the strength of 

 the stimulus. Stimulation of the foot disk, either at the edge or on 

 the lower surface, produces local contraction of the foot and base 

 of the column, and acontia are usually emitted near the point stimu- 

 lated. The tentacles may contract also, but always as a whole, the 

 same general reaction following stimulation at different points of 

 the disk instead of a local reaction as in the cases of the foot, 

 column and acontia. This inability of the tentacles to recognize 

 the direction of the stimulus is also characteristic of the reaction 

 of the tentacles of Coryuwrpha to stimulation of the column, and 

 is due, I believe, to the opportunities for diffusion of the stimu- 

 lation impulse owing to the distance of the reacting structures 

 from the point at which the stimulus is applied. 



The entire surface of 5. davisi, with the possible exception of 



