278 PROTOPLASM 



and a gradual transition between the non-motile layer of the 

 wall and the streaming protoplasm, and that therefore the 

 relations are here, as a matter of fact, essentially different 

 from the case of a snail's foot, which moves upon a firm 

 substance completely separated from itself. Further, if the 

 relations were as supposed, one would expect to observe in 

 the rotating protoplasm something of the wave of con- 

 traction that would move forward, which would, of course, 

 be marked out towards the cell-sap cavity as projections, just 

 in the same way as distinct waves of contraction are to be 

 traced in the snail's foot. Finally, the observation of these 

 streaming processes teaches us quite definitely that there 

 is certainly no creeping substance present in the way in 

 which Engelmann's explanation 'supposes, but that we are 

 dealing with a substance which is flowing — a fact which can 

 be traced' very plainly in the movements, displacements, 

 torsions, etc., which the particles contained in the streaming 

 protoplasm go through. 



Hence, as has been said, the hypothesis of Engelmann 

 also seems to me to give no satisfactory idea of the causes 

 and mechanical relations of protoplasmic movements, just as 

 little as the two before-mentioned molecular hypotheses were 

 able to do. On the whole, I believe that, as Berthold has 

 declared already, nothing profitable is to be obtained by 

 setting up peculiar molecular hypotheses to explain certain 

 ' processes in the organic world. At any ra;te it seems to me 

 much more ptomising and satisfactory to seek for the causes 

 and conditions of these processes among the known physical 

 forces than to have recourse to special molecular forces 

 constructed ad hoc. It is only necessary to call to mind, 

 for example, the complication of the assumptions made by 

 Sachs — and those of Engelmann are in like manner very 

 complicated, since he also postulates an increase and decrease 

 of the attractive forces of his inotagmas corresponding to 

 the decrease and increase of their water of imbibition, that is 

 to say, of the watery envelopes of the inotagmas — in order 

 to convince oneself that it would be difficult to attain to 

 satisfactory explanations in this direction. 



