THE WONDERS OF LIFE 



ance of real, nucleated cells. Hence we have to distin- 

 guish two different forms of movement in the unicellular 

 organism — the inner movement in the caryoplasm of the 

 nucleus and the outer in the cytoplasm of the cell-body; 

 the two enter into close mutual relations during the 

 remarkable process of partial resolution of the nucleus 

 (caryolysis). In this modification and partial dissolution 

 of their constituents we observe, during indirect cell- 

 division, certain complicated movements (the signifi- 

 cance of which is as yet entirely unknown), that are 

 accomplished by both the granules of chromatin and the 

 threads of achromin, and which are comprised under the 

 head of nuclear movements (caryokinesis). It has lately 

 been attempted to explain them on purely physical 

 principles. The same may be said of the internal flow 

 of the plasm which we find in the plasmodia of the 

 amoebae and mycetozoa, and in the endoplasm of many 

 of the protophyta and protozoa 



The slow displacement of the molecules of plasm 

 which is at the bottom of these plasma-movements also 

 causes a variety of external changes of form in simple 

 naked cells. Variable processes like folds or fingers 

 (the "fold-feet," lobopodia) appear on their surface. As 

 they are best observed in the common amoebae (naked 

 nucleated cells of the simplest kind), they are called 

 amoeboid movements. With these is connected the 

 variable movement of the larger rhizopods, the radiolaria 

 and thalamophora, in which hundreds of fine threads 

 radiate from the surface of the naked plasma-body. A 

 number of recent experts on the rhizopods, such as 

 Biitschli, Richard Hertwig, Rhumbler, and others, have 

 attempted to trace to purely physical causes this vary- 

 ing formation of pseudopodia, and their branching and 

 netlike structure (without definite direction). 



It is more difficult to do this in the case of the most 

 highly differentiated of the protozoa, the infusoria. 



268 



