332 MOTOR RESPONSES 



posite sides, the one facing the anode, the other the cathode; and that 

 either or both of these two sets of changes may result in what is usually 

 called a response, although not necessarily an orienting response. Thus 

 while the motor responses in these organisms usually occur at the catho- 

 dal side when the circuit is closed, Kiihne (1864), Verworn (1895), 

 and McClendon (1911) observed in Amoeba and other rhizopods con- 

 traction at the anodal side. In some of these organisms, the anodal con- 

 traction appears to be involved in streaming toward the cathode; but 

 there are other anodal responses which obviously have nothing to do with 

 locomotion. For example, Loeb and Budgett (1897) assert that there is, in 

 Amhlystoma, copious secretion of mucus on the anodal side. Moore 

 (1926) obtained bioluminescence and contraction on the anodal side of 

 the Ctenophores, Mnemiopsis, and Beroe. Lyon (1923) and Lund and 

 Logan (1925) observed, in Noctiluca, a sort of contraction first at the 

 anodal side and later also at the cathodal side, and sometimes the reverse. 



In all of the organisms referred to above, except Noctiluca, the 

 anodal responses differ radically from the cathodal responses. This is 

 very evident from the results of observations on Amoeba, in which it 

 can be clearly seen that, after the circuit is closed, there is first local 

 liquefaction of the plasmagel on the cathodal side, then contraction, 

 and finally cytolysis on the anodal side. In Volvox, however, the response 

 on the cathodal side in colonies which are positive to the cathode, is, in 

 all perceptible characteristics, precisely the same as the response on the 

 anodal side in those which are positive to the anode. Here, then, is an 

 actual reversal in the action of the current, i.e., an actual reversal of 

 Pfliiger's law. Closing the circuit apparently produces the same effect 

 on the anodal side of colonies in certain physiological states as it does 

 on the cathodal side of colonies in other physiological states. 



These physiological states are, as set forth above, specifically associated 

 with those involved in reversal in the direction of photic orientation. As 

 demonstrated above, these are dependent upon illumination, tempera- 

 ture, and chemicals in the environment, which apparently control the 

 electric charge carried by the colonies and the bodies within them. What 

 is much needed now is a more comprehensive study of these charges, 

 in relation to the chemical and the physical content of the environment 

 as well as the character of the responses of the colonies. 



