36 THE ELEMENTARY NERVOUS SYSTEM 



purely amoeboid. It seems to represent a stage of differ- 

 entiation between amoeboid motion and simple muscle con- 

 traction which may well indicate the kind of contractility 

 that the common flesh of the sponge possesses. But 

 wherever these two types of tissue belong, they certainly 

 both exhibit nothing in their activities that suggest a 

 coordinating system. They act with great independence 

 and as though they were stimulated directly, and in this 

 respect they exhibit all the characteristics of indepen- 

 dent effectors. 



