292 F. W . Bancroft. 



It is evident that these phenomena lend themselves very nicely 

 to Loeb's^ explanation of galvanotropism, which he considers de- 

 pends on similar changes in the tension of associated groups of 

 muscles. The constant flow of the current brings about an in- 

 crease of tension on the cathodal side of tentacles and manubrium, 

 as a result of which this part is more strongly contracted than the 

 anodal portion. When the tentacles are exhausted the anodal 

 part may even be completely relaxed, 



Greeley- has stated that when "Gonionemus was exposed to the 

 constant current, rhythmical contractions began always on the 

 cathodal side when the medusa was immersed in normal sea 

 water, but that the contractions began on the anodal side in acidu- 

 lated sea water." A series of experiments was made on Polyor- 

 chis to test its behavior in acid and alkaline sea water, but as long 

 as the tentacles were sufficiently uninjured so that they responded 

 at all to the current, they behaved as above described, «o matter 

 what the reaction of the water. The influence of acid and alka- 

 line media on the contraction of the muscles was also tested, but 

 Greeley's results could not be confirmed. Usually a change in 

 the reaction of the sea water made no difference, and even when 

 it did the change in the electrical response was sometimes in one 

 direction and sometimes in another, so that no significance could 

 be attached to it. 



As a rule the muscles of a meridional strip of Polyorchis do not 

 behave towards the galvanic current as described by Greeley for 

 Gonionemus in normal sea water; for the place of maximum re- 

 sponse is the anode. It is here that the contractions usually start 

 and here that the most rapid rate of the rhythmic contractions is 

 usually seen. But there is such an abundant opportunity for stim- 

 ulation at secondary cathodes that I am not yet prepared to say 

 that we have here an exception to Pfliiger's law. 



Berkeley, April 9, 1904. 



_ ^Loeb. J., 1897, Zur Theorie der physiologischen Licht und Schwerkraft- 

 wirkungen. Pfliiger's Archiv. Bd. 66, p. 440: 



-Trelease, W., 1903. Report of a meeting of the Academy of Sciences of 

 St. Louis. Science, N. S., Vol. XVIII, p. 753. 



