102 SCIENCE PROGRESS. 



of current, thus indicating the general direction of equi- 

 potential curves (which we know to be at right angles to 

 the lines of current). 



A curious sight is offered by the behaviour of a drop of 

 hay-infusion, containing paramcecia in sufficient abundance, 

 placed in a fiat vessel into which dip the unpolarisable elec- 

 trodes of a battery of 2 to 5 volts. At make the whole crowd 

 of paramcecia fall into order with their noses towards the 

 kathode, and begin to swim towards it in converging curves ; 

 in a few minutes they are thickly crowded round the kathode, 

 and the fluid round the anode is quite cleared ; if now the 

 direction of the current is reversed, the crowd breaks up, 

 all its units turn round and begin to swim away as if of one 

 mind from the new anode to the new kathode, to which the 

 crowd converges as before. 



There does not seem to be any unanimity among the 

 protozoa as to the direction they shall adopt in relation to 

 the current. Paramcecia swim with the current from anode 

 to kathode ; in this little electric bath you can follow them 

 with the naked eye, but I will throw them upon the screen, 

 when you will see them better still. As I put on the cur- 

 rent they turn with one accord to the kathode and swim to 

 the kathodic bank of their lake, as I reverse the current 

 they turn round and swim over to the other bank ; there 

 happen to be not very many paramcecia in this infusion. 

 What is happening on the screen is absurdly like what one 

 may see in the country ; these little brown spots swimming 

 across their lake from bank to bank look just like rabbits 

 scampering across a field from one cover to another, and as 

 we reverse the current they scurry across backwards and 

 forwards as if beaten out of cover as soon as they have 

 found it. If one reverses the current at a moment when 

 they are scurrying across at the top of their speed, they 

 turn themselves and rush off the other way. 



Ciliated infusoria, as a rule, agree with paramcecia and 

 swim with the current. The custom among flagellata, on 

 the other hand, is to swim the other way ; they affect the 

 anode or the anode affects them. It is difficult to resist 

 laughing when one has under one's eyes the spectacle of a 



