NOTE ON THE GALVANOTROPIC REACTIONS OF 



THE MEDUSA POLYORCHIS PENICILLATA 



A. AGASSIZ. 



BY 



FRANK W. BANCROFT. 



(From the Rudolph Spreckels Laboratory of the University of California.) 



Comparatively few papers on the galvanotropic reactions of 

 coelenterates have been published and so far as I know there are 

 only two bearing directly on the questions here considered. The 

 first is by PearP, who finds that when any, except the very strong- 

 est, galvanic currents are passed transversely through hydra the 

 animal contracts most strongly on the anode side so that the 

 free end — which may be either oral or aboral — swings around 

 and points towards the anode. The tentacles, however, behave 

 differently. With weak currents only those tentacles which are 

 parallel to the current lines contract, but of these the one towards 

 the cathode has a tendency to contract most strongly. When the 

 whole animal has become oriented the tentacles curve slightly so 

 as to become concave on the side towards the cathode. The sec- 

 ond observation is by Greeley and will be considered in detail 

 later on. 



The tentacles and manubrium of Polyorchis penicillata, which 

 occurs abundantly in San Francisco Bay during certain seasons 

 of the year, furnish excellent material for the demonstration of 

 galvanotropic reactions, responding to the current in some re- 

 spects like the tentacles of hydra, but with greater distinctness. 

 The method of experimentation consisted in cutting the medusae 



iPearl, 1901, Studies on the Effects of Electricity on Organisms. II. — The 

 Reactions of Hydra to the Constant Current. Amer. Jour. Physiol, Vol. V, 

 PP- 301-320. , 



