HABITS AND REACTIONS OF SAGARTIA DAVISI. 2O/ 



The result of the second reaction is varied. Often the tentacle 

 merely waves stiffly inward. At other times it may arch so that 

 its point is directed toward the mouth. On the whole, however, 

 its movements are less definitely adaptive than those which 

 Parker describes for Mctridimn. 



The second reaction does not always follow the first. The 

 general contraction does not appear to be induced by contact 

 alone. If the tentacle be touched lightly and for but an instant, 

 only the first reaction occurs. If, however, the stimulating ob- 

 ject rest against the tentacle sufficiently long to allow the latter 

 to adhere to it, the second reaction immediately follows. Whether 

 this results from the adhesion itself, or the duration of the stimu- 

 lus, or a tension in the muscles due to the resistance of the 

 stimulating object, I am unable fully to decide. Such small ob- 

 jects are capable of producing this reaction that the third possi- 

 bility seems to be excluded. Whichever of the other two be 

 the efficient stimulus, it produces a strong contraction of the 

 muscles directly affected. This strong contraction probably 

 serves as a direct stimulus for contiguous muscles, the contrac- 

 tion of these for others, and so on, until all are involved. In no 

 case did the evidence enforce the assumption of the presence of 

 nerves, in the tentacular responses. 



So far the movements of but a single tentacle have been con- 

 sidered, without relation to the others. And it should be said 

 here that tentacles cut from the polyp behave in all essential 

 respects as they do under normal circumstances. Often the 

 stimulus applied to one tentacle is sufficient, unless care be used, 

 to induce contractions in several. It may be that only a few 

 tentacles on each side of the one touched will react ; with a 

 stronger stimulus the entire set of tentacles may contract with 

 vigor. There is no more evidence, however, that this correla- 

 tion of parts is attained by the aid of nervous tissue than there 

 was in the case of the single tentacles. Communication from 

 one tentacle to the next is largely through the oral disk. 

 The proper degree of contraction of a tentacle induces a con- 

 traction in neighboring muscles in the oral disk, and pos- 

 sibly in contiguous tentacles directly. The vigor of the stim- 

 ulus, if it be local, appears to determine the extent of the 



