694 



EAYMOND PKAHL. 



the Infusoria, and to fiiul the samo tiling in a multicollular 

 organism is a matter of considerable interest. It is out- 

 side the scope of the present paper to discuss the relation 

 of this result to current theories of electrotaxis, as I hope 

 to be able to do in a later paper, but it may be said that 

 this furnishes another strong piece of evidence that in the 

 case of these loAver organisms the current does not cause the 

 observed reactions in any way comparable to that in which a 

 mechanical stimulus causes a reaction, i. e. by furnishing a 

 certain "sensation." On the contrary, the current acts as 

 a physical force on a structure organised in a certain way. 

 Experiments on the electrotactic reaction of cut pieces of 



lfy^^yyy^^--y^^A~,-~^ .^^^^^y^ ^^, 





Fig. 4S. — Diagram sliowiii^ (he electrotactic reaction of the rhabdocele, 

 St en OS to ma leucops, O. Schm. 



planarians have been tried in considerable numbers, but Avith, 

 on the whole, unsatisfactory results. Anterior pieces result- 

 ing from transvei'se cuts are the only ones from which I have 

 been able to obtain any constant results. Such pieces react 

 like the normal animal in every way. Posterior pieces from 

 transverse cuts show the contractions on the anode side and 

 ends in a slight degree, but there is no constant production 

 of orientation. Specimens slit longitudinally in the middle 

 line from the posterior end nearly to the head react 

 essentially like a normal specimen, although much more 

 weakly. I have observed in one case fairly precise orienta- 

 tions of such a specimen. From specimens slit longitudinally 



