466 G. H. PARKER 



been unable to find even a slight difference between these two 

 sets of nematocysts such as might be inferred to exist from the 

 table given by Glaser and Sparrow ('09, p. 367). 



Whien the portion of the tentacle or acontium that receives 

 an effective stimulus is compared with that from which the 

 nematocysts are discharged a striking condition is found. With 

 mechanical stimulation the nematocysts are discharged only 

 in the immediate region of the application of the stimulus, 

 as observed long ago in Cordylophora by Schulze ('71); with 

 chemical stimulation apparently the same is true. If the dis- 

 tal end of a fragment of an acontium or a tentacle is treated 

 with dilute acid, the nematocysts are discharged at that end 

 and nowhere else. If the proximal end is similarly treated, 

 they explode only in that region. There is thus no evidence 

 in these two organs of nervous transmission in either direction 

 so far as the nematocysts are concerned. But the relation of 

 the stimulated area to the area of discharge is best seen when 

 the stimulus used is a colored fluid such as methjd green. If a 

 small crystal of that kind of methyl green which will cause the 

 discharge of the nematocysts is brought near a living acontium, 

 the nematocysts can be seen to explode as they become covered 

 by the diffusing green solution and as they are never discharged 

 in advance of the cloud of colored fluid, the evidence for the 

 local action of the stimulus uninfluenced by transmission, is 

 very conclusive. 



These observations are in exact agreement with those of Wag- 

 ner ('05, p. 618) on Hydra and I therefore conclude that nema- 

 tocysts are discharged by a local stimulus and not by an impulse 

 that has been transmitted from a distance. Is this local action, 

 however, of a direct kind or does it involve a minutel^^ circum- 

 scribed nervous mechanism? Such a question is not to be 

 answered by localized stimulation but must be approached bj' 

 other means. Two drugs are known which completely abolish 

 nervous activity in many lower animals, including the actinians, 

 and which therefore may be used in testing this matter. They 

 are chloretone and magnesium sulphate. 



