318 PROTOPLASM 



with those of the drops of oil-lather, I was necessarily the 

 more astounded when it was shown by observation of the 

 Pelomyxa creeping in water, with which Indian ink or ivory 

 black had been mixed, that currents, directed in the same sense 

 as the superficial protoplasmic streaming movements, do not, as 

 a matter of fact, exist in the surrounding water. If the stream- 

 ing movements of the Pelomyxa are not very powerful, it really 

 does appear as if no currents at all went on in the surrounding 

 water, as stated by Berthold. If, however, one observes closely 

 the anterior end of a Pelomyxa streaming forward very ener- 

 getically, or a pseudopodium which is developing powerfully, 

 it can be made out that currents do exist in the surrounding 

 water, but, strange to say, currents which run in exactly the 

 opposite direction to what was expected, and which do not 

 pass along in the same sense as the superficial back current at 

 the anterior end, but in a reverse direction, that is to say, they 

 rush towards the anterior end, i.e. towards the supposed centre 

 of extension. Considering the importance of the matter, I have 

 not left it to be judged by the eye, which might easily be 

 deceived, but have definitely traced the existence of these 

 currents with the ocular micrometer. I will take this oppor- 

 tunity to state again, that in streaming drops of oil -foam of 

 larger size I have frequently convinced myself of the presence of 

 currents running in the same sense. 



I do not underrate the consequences of these results. They 

 necessitate the admission that the explanation of amoeboid 

 movement brought forward by me above is inadequate, i.e. that 

 in it there must at least be one discordant point, in which 

 Amwbce behave differently from the drops of oil -foam. I have 

 already remarked that the study of the movements of Pelomyxa 

 shows in other respects so complete a similarity to those of the 

 oil-foam drops apart from the divergence that has been pointed 

 out that I cannot doubt as to the identity of the forces in 

 operation in both cases. Unfortunately I am not in a position 

 to give an explanation of this difference off-hand. In any case 

 all that I can suppose is somewhat as follows. Perhaps the 

 behaviour which we have described in the Pelomyxa points to 

 the fact that the surface of the protoplasmic body is enveloped 

 by an extremely fine, viscid layer of a chemically different 

 nature, such as Quincke has assumed in the oil membrane, and 

 that further the forces of tension which are at work make their 

 appearance, as he supposes, at the limiting surface between this 

 membrane and the protoplasm below. Under these conditions 

 it may perhaps be imagined that the backward current which 

 is necessarily present may go on in the internal zone of this fine 



