EXPERIMENTS ON WORMS 95 



is gained, however, by making such a statement. We 

 wish to know how the supraoesophageal ganglion can 

 inhibit movements, and how its absence can increase 

 spontaneity. 



It is not possible to offer at present more than a 

 suggestion. We can increase and decrease the loco- 

 motor activity of a jelly-fish at desire by changing 

 the constitution of the sea-water. If we increase the 

 number of Na ions in the sea-water, the rate of rhyth- 

 mical contractions in Gonionemus increases and the 

 animal becomes restless. If the number of Ca ions 

 be increased, the animal becomes quiet. It is, more- 

 over, a fact that the different parts of a Gonionemus 

 are affected somewhat differently by the same ions, 

 inasmuch as the margin is more immune against the 

 effects of Ca ions than the centre. I think it possible 

 that there is a similar difference between the segments 

 belonging to the supraoesophageal and subcesopha- 

 geal ganglion. It might be possible that the ions 

 (or some other substance) of the blood influence the 

 supraoesophageal ganglion or its segments in such a 

 way as to cause a decrease in the locomotions, while 

 the same constituents of the blood do not have such 

 an effect upon the subcesophageal ganglion or its 

 segment. But the blood is not the only agency 

 which is to be considered in this connection. The 

 supraoesophageal ganglion of Annelids is connected 

 with the alimentary canal by nerves. The processes 

 which go on in the intestine that is, the chemical pro- 

 cesses of secretion and digestion can only affect the 



