MOVEMENT AND CONTRACTILITY 267 



7. The. Phenomena of Protoplasmic Movement in their 

 Relation to the Alveolar Structure 



(a) Theories as to the Causes of the Phenomena of Movement 



In my review of 1891 I had. already pointed out that 

 the great similarity between the phenomena of movement 

 of the foam-drops and the simpler locomotory phenomena of 

 protoplasmic structures, is further evidence for the correctness 

 of my view with regard to the structure of protoplasm. For 

 these and other reasons it therefore seems necessary that we 

 should give some attention to these relations ; that is to say, 

 that we should consider rather more closely both the 

 phenomena of movement and previous attempts to explain 

 them. 



(6) So-called Contractility 



For a long time back the view has been consciously or 

 unconsciously held that all the phenomena of movement 

 exhibited by protoplasmic bodies are to be referred to the 

 same fundamental property. Under these circumstances it 

 was natural that the form of movement hitherto most 

 familiar to us, namely, the contraction of muscle protoplasm, 

 should be claimed as this fundamental property, and an 

 attempt be made to derive all phenomena of movement from 

 it. Since, therefore, the older attempts to explain the pheno- 

 mena of streaming and movement in simple protoplasmic 

 bodies as the result of electrical or chemical forces, etc., 

 did not lead to a successful issue, it was thought that the 

 key to the comprehension of these protoplasmic movements 

 was to be found in the so-called contractility of protoplasm, 

 which itself was not to be further explained.' From the 

 facts of the genetic development of organisms it might 

 perhaps have been predicted that a correct explanation ought 

 rather to take the opposite path, since the typically con- 

 tractile protoplasmic structures are undoubtedly not the 

 most primitive, but have developed at a much later stage. 

 The solution of the problem would, as has been said, have 



