2(;o PROTOPLASM 



always kept this problem in view; and tlie firm conviction 

 thiit then- was in this direct ion a prospect of arriving at a 

 comprehension ,.f protoplasmic movements was one of the 

 main incentives of the investigations described in this work. 



In ISSO liindfleisrh published his ideas upon the 



supposed causes of protoplasmic movements, which have 



certain points in common with the view that surface tension 



comes into play in this process. Rindtleisch adopted the 



theory of the reticular framework of protoplasm, and sought 



to show that the intimate interpenetration of two different 



substances, />. the framework and the intervening matrix, 



which follows from such a structure of protoplasm, was of 



fundamental importance for the origin of processes of 



movement. His hypothesis asserts that the adhesion of the 



two interpenetrating substances forms the active principle 



in the origin of processes of movement; alterations of their 



adhesion necessarily produce small movements, the sum 



total of which bring about the observed effect. He tries to 



support this assumption by reference to the phenomena of 



movement in fluids. For instance, he refers to the movements 



which a drop of glacial acetic on a slide, or a fine layer of 



oil on water, shows when warmed. In these cases, however, 



there is no doubt that surface tension is the cause of the 



changes of form and phenomena of movement, so that it 



may well be supposed that Eindfleisch had in reality 



imagined this to be if anything the efficient cause. Besides, 



it scarcely requires any special discussion to show that no 



explanation is possible in the way indicated by him, since 



the hypothesis of a reticular framework, which nevertheless 



must be fluid, in order to exhibit changes of form and 



phenomena of movement under the assumed conditions, does 



not seem possible. 1 



In the year 1886 Berthold arrived at the view that the 

 protoplasmic streamings in vegetable cells had their cause in 



1 It may bo mentioned here quite briefly that Geddes (1883) developed a 

 hypothesis which socks to refer aimvboid movement and the contractions of 

 striped muscles to the so-called phenomena of aggregation, such as Darwin 

 observed in the protoplasm of insectivorous plants. Geddes's view is not, 

 however, perfectly intelligible to me. 



