MECHANISM IN SEA-ANEMONES. 343 



relation to the stimulus and so invariable in its occurrence that it 

 must be regarded as a true reflex and as an example of such an 

 operation it certainly compares very favorably with what is often 

 seen in many of the higher animals. 



The muscular reactions of the sea-anemones are then by no 

 means all of a kind, but range from direct muscle responses of a 

 most primitive character to true reflexes. The more complex 

 operations of these animals such as food-taking, creeping, and so 

 forth, are not to be regarded as the result of the action of a rela- 

 tively uniform neuromuscular mechanism, but depend upon some 

 combination of the various types of muscular or neuromuscular 

 activity possible to these animals. These operations are often ex- 

 tremely complex and call for a high degree of coordination and yet 

 this coordination is almost entirely of local origin, for an isolated 

 tentacle will react to food almost exactly as an attached one does 

 and the pedal disc, even after the oral disc has been cut away, will 

 creep in a fashion indistinguishable from that of a whole animal. 

 There is therefore good grounds to agree with those who maintain 

 that the nervous system of the sea-anemone is essentially dift'use 

 lacking obvious centralization. 



Harvard University, 

 April, 1916. 



