CURRENTS IN PLANT CELLS 327 



fibril, or rather a contractile column, which consists of a 

 single layer of alveoli ; the same action will be manifested 

 in the same way, if the column consists of a double layer of 

 alveoli. The conditions are less favourable if the muscle 

 column is more than two layers of alveoli in thickness, 

 because the alveoli are no longer all in contact with the 

 sarcoplasm. 



I think I have shown in the foregoing that, on the basis 

 of our conception of protoplasmic structure, the possibility is 

 conceded of an insight into the mechanics of muscle con- 

 traction. I am of course far from regarding what has been 

 put forward as a theory of this process. I see only a guide- 

 post, as it were, in the direction of a future theory, which 

 will require the joint labours of many to follow it u^ or set 

 it aside, as the case may be. Yet there appears to me to 

 be one further point, in the supposition put forth above, 

 which is worthy of special consideration. As is becoming 

 more and more evident from recent observations upon 

 the structure of muscle cells, a peculiar interpenetration 

 of two substances, i.e. of the contractile elements and the 

 so-called sarcoplasm, is especially characteristic of them. I 

 am not aware that any one of the views that have been 

 held hitherto upon the mechanics of contraction gives an 

 idea of the significance of this peculiarity, while we see, on 

 the other hand, that the hypothesis set forth above is able 

 to explain this very point to a certain extent. 



(ri) Rotational Currents in Plant Cells 



As we remarked before in discussing Berthold's views, 

 the so-called rotational streaming movements, which occur 

 fairly commonly in plant cells, are especially difficult to 

 comprehend. It has already been declared above that I am 

 unable to agree with the remarks of Berthold upon the 

 origin of this process. Although I have not studied this 

 subject thoroughly myself, nevertheless it seems to me 

 worth while adding a few remarks upon this point ; that is 

 to say, to discuss the possibility, at least, of explaining this 



