274 PROTOPLASM 



neighbouring ones, for the water envelopes depend on the 

 force of the affinity for water possessed by the molecules 

 remaining in statu quo; and since this force is not 

 disturbed or altered in the adjacent molecules, I do not 

 see how a current of water can be brought about in the 

 manner alleged. I am hence of opinion, both from these and 

 other reasons, that a comprehension of the most simple proto- 

 plasmic movements is not to be arrived at in the way 

 which Sachs considers possible, and still less so in the 

 case of the more complicated instances of pseudopodial 

 development, etc. 1 



In 1879 Engelmann put forward the hypothesis that 

 the cause of the phenomena of movement exhibited by 

 protoplasm was to be sought in the contraction of its 

 minutest particles, the so-called " Inotagmas," which are to 

 be conceived of as " combinations of molecules." These 

 inotagmas are supposed to possess an elongated form when 

 in a state of rest, and during the contraction following upon 

 stimulation to approach a spherical form more or less. 

 Their contraction itself is supposed to depend upon an 

 alteration in their state of turgidity, since it is prob- 

 able that with increased turgidity they would tend to 

 shorten, or on the other hand, after giving off fluid, to become 

 stretched again. The latter assumption, therefore, brings 

 Engelmann's theory near to that of Hofrneister and Sachs 

 to a certain extent, from which it differs essentially with 

 regard to the mechanical explanation of the processes of 

 movement. I am, however, of the view that Engelmann's 



1 A special micellar theory of the movements of protoplasm was also 

 developed by the botanist C. Kraus in 1877. I think I need not discuss it 

 here more particularly, but will content myself with the remark that Kraus 

 starts from the assumption that the attraction of the micellse, both among 

 themselves and for the water of their envelopes, depends on the relation of 

 their volume to their surface. With diminution of the volume of the 

 micellse their mutual attraction diminishes more rapidly than their affinity 

 for water ; hence the protoplasm becomes more watery. During the increase 

 in size of the micellse, on the other hand, their mutual attraction would 

 increase to a relatively greater extent, which would necessitate an approxima- 

 tion of their middle points, and at the same time a contraction, which would 

 he able to produce phenomena of movement, changes of shape, processes of 

 division, formation of vacuoles, etc. 



