214 



from a variety of observations he concludes that Nagel is quite wrong. 

 He found also, as we do, that the base of Actinia is the region of max- 

 imum sensitiveness to contact. Parker (1896) found that the tentacles 

 of Metridiimi are not noticeably affected in any direct fashion by soluble 

 food. Torrey (1904) on the other hand says that the tentacles of Sa- 

 gartia davisi show very definite adaptive reactions and can distinguish 

 between mechanical and chemical stimuli, making even certain choices 

 in the quest of food. 



Our conclusions approximate much more closely to those of Loeb 

 and Davis than to those of Nagel and Torrey. The tentacles do cer- 

 tainly show some amount of characteristic reaction to chemical stimuli 

 for, when tried with strong bovril or meat extract, those immediately 

 affected are set on the move. If the solution used is very strong, we may 

 find rapid contraction of the tentacles affected. Solutions applied to 

 the mouth caused the lips to open immediately and led to movements 

 of the tentacles more or less all round; if, on the other hand, tentacles 

 are tested only those in the immediate neighbourhood are moved. If 

 fairly strong solutions are placed against the base of a horizontally 

 extended Anthea, the animal bends its tentacles and disk towards the 

 stimulated region. Very strong solutions cause rapid contraction but 

 such reactions are quite out of the ordinary course of the animal's life, 

 so no great importance should be attached to them. We find then, so 

 far, that the mouth region possesses the maximum sensitiveness for 

 chemical stimuli, that the edge of the base is also sensitive, but that the 

 sensitiveness of the tentacles for this type of stimulus is almost nil unless 

 the extract used is unnaturally strong. 



In Anthea cereus some of the tentacles are constantly on the move, 

 and if any object is left in their field, they are fairly sure to touch it 

 sooner or later , but we cannot say that the tentacles show any reaction 

 at all to chemical stimuli due to food set for them in this way; it is in 

 every case evidently a haphazard movement leading ultimately to contact. 

 In other sj)ecies, and especially in Actinia^ the tentacles move less and 

 demonstrate the same conclusion much more effectually. 



If a piece of fresh raw meat, or of paper soaked in meat extract be 

 suspended over the mouth of Actinia or Anthea and fairly close to the 

 disc, the tentacles begin to move about in all directions after the mouth 

 has started opening. If meat be placed near the tentacles of Actinia^ 

 they will be affected only if and when the juices of the meat have 

 stimulated the edges of the mouth unless they chance to wander into 

 contact with the food. In all cases it seems evident that the special region 

 of sensitiveness to the more ordinary and likely chemical stimuli is the 

 mouth, not the tentacles. 



