324 PROTOPLASM 



these circumstances it seems certain, therefore, that in 

 foam-like protoplasm local alterations of the tension of 

 certain lamellae must produce immediate changes in the 

 shape of the alveoli, such alterations of tension being caused 

 either by the granules of the protoplasm or by something 

 else. In this way it becomes very probable that the 

 granules, if they possess the properties attributed to 

 them, may also give occasion to phenomena of movement in 

 the interior of the protoplasm, but that numerous other 

 causes also, which produce a change in the tension of 

 certain lamellae, are able to take effect in a similar manner. 

 For it is to be expected that every chemical change 

 in the protoplasm of the lamellae, as well as in the contents 

 of individual alveoli, will alter the tension of the lamellae, 

 and that in this way changes of shape and consequent 

 displacements of the alveoli must continually take place. 



It seems to me therefore very probable that the irregular 

 undulating movements to and fro, which are to be observed 

 in nearly all protoplasm, depend on the causes which have 

 been named, and that, in fact, they are inevitable, so to 

 speak, if the conceptions which I have developed with 

 regard to protoplasm are admitted to be correct. 



Whether these internal processes of movement, to which 

 I have already referred in 1888 (see Protozoa, p. 1397), 

 can also develop into regular streaming movements, seems 

 to me doubtful ; nevertheless I would not altogether deny 

 this possibility in the case of the phenomena of streaming 

 movement in the endoplasm of Ciliata. Since there is in 

 these forms no cell-sap cavity, which in plant cells, as we saw 

 above, is of great importance for the appearance of extension- 

 currents, we are in this case only able to indicate the mouth 

 opening as the region where such currents originate, since it 

 is here that the endoplasm usually comes into contact with 

 the surrounding water. Although I do not consider it 

 possible that an extension-current, starting from this point, 

 and as a rule only taking effect upon one side, is sufficient 

 to explain the circulation of the endoplasm of the Ciliata, I do 

 not wish to enter more thoroughly into the point, since so to 

 do could not be productive of much result without a special 



