62 THE ELEMENTARY NERVOUS SYSTEM 



to their original position in the interior of the animal. 

 This withdrawal is accomplished chiefly by the action of 

 the cilia on the acontia, which form an extensive band on 

 each of these filaments and beat in such a direction as to 

 carry the acontium through the seawater toward its at- 

 tached base. 



When the acontia are fully extended in the external 

 seawater, and perhaps also after they are withdrawn 

 within the sea-anemone, they may exhibit more or less 

 continuous, slow, serpentine movements. These move- 

 ments are due partly to their cilia and partly to a strand 

 of muscle fibers that extends lengthwise their axial re- 

 gion and is known as the longitudinal muscle of the acon- 

 tium. It has been claimed that this acontial muscle has 

 parallel and close to it a delicate band of nervous tissue, 

 but, for the following reasons, this does not seem to be 

 true. Pieces of acontia four to five centimeters long can be 

 easily obtained from a large sea-anemone and will con- 

 tinue alive and active in seawater for many hours. When 

 such filaments are mechanically stimulated by agitating 

 them in seawater or by dropping seawater on them, or 

 when they are flooded with dilute meat juice, they twist 

 themselves into irregular coils. This response takes place 

 slowly and only after a minute or two. If the stimulus is 

 limited to one end of a long acontium that end and that end 

 only responds by becoming coiled. This reaction will 

 occur as well at the central end as at the peripheral end of 

 a given acontium. When acontia have been kept for 

 twenty minutes or so in seawater containing chloretone, 

 a period long enough to anesthetize the tentacles of an 

 intact sea-anemone, they will still become coiled when 

 flooded with dilute meat juice exactly as unanesthetized 

 acontia do. When acontia still attached to a sea-anemone, 



