GALVANOTROPISM OF TADPOLES. 99 



ments are, so to speak, more dead beat, and, in the absence 

 of current, or even while the current is passing, the position 

 of the long axis remains stable in any position, preferably 

 antidrome, i.e., with head to anode, but frequently homo- 

 drome, with head to kathode. In the antidrome position, 

 as you may see, they are perfectly still as if paralysed, in 

 the homodrome position they wag their tails. I wake 

 them up by reversing the current ; after a dart here and 

 there they settle again and it may be in any position. 

 Both may look up stream or down stream, or one may 

 look one way, the other the other. And now, to quickly 

 realise the relation between direction of current and posi- 

 tion of tadpole, I am sure from my own hesitation, in spite 

 ol the pointer showing how the current is going, that you 

 do not instantly recognise the sudden changes under the 

 correct rubric, "homodrome," "antidrome". So let me use 

 domestic language, and, comparing our tadpoles with cats, 

 speak of the current as stroking them the right way, viz., 

 from head to tail, or stroking them the wrong way, from 

 tail to head. 



You will, I think, readily admit a valid excuse for such 

 untechnical language when you have recognised by a rapid 

 series of trials that stroking the right way pacifies, stroking 

 the wrong way excites, i.e., in technical language, arrest by 

 an antidrome current, excitation by a homodrome current. 

 The tadpoles happen to be lying side by side and I cautiously 

 stroke them the wrong way by gradually putting on current 

 with the screw-rheostat, they both wag their tails. I 

 cautiously reverse the current, unscrewing the rheostat, 

 reversing, then screwing again, guiding myself as to cur- 

 rent-strength by the current indicator ; the tadpoles, which 

 are now being stroked the right way, lie perfectly still. Or 

 better still, having been stirred up to greater activity by 

 sudden reversal or reversals of current, they have come to 

 rest side by side with their heads in opposite ways ; and 

 now I am able to play at see-saw, by cautiously putting on 

 current and cautiously reversing it. Always the tadpole 

 stroked down the wrong way wags his tail, while his 

 companion, who is at the same time being stroked down 



