Some Questions which they Suggest. 21 



The plasmodium is differentiated into two parts: the 

 larger and interior part contains minute oil granules, or 

 microsomata ; the external layer is free from granules, and 

 is perfectly transparent like glass or water. The darker 

 and granular interior protoplasm is known as the endoplasm; 

 the hyaline superficial layer is known as the ectoplasm. 

 Fig. 4 is on too small a scale to exhibit this difference 

 distinctly. 



There are two motions here to be observed, though they 

 are not disconnected with one another : first, the pulsating 

 motion of currents of protoplasm ; and, secondly, the 

 advance of the entire mass of protoplasm. 



Under a microscope currents are seen to be established 

 in the endoplasm, generally up or down the lines of advance 

 of the plasmodium ; the letters st in Fig. 4 indicate some 

 of these currents. The granules stream in one direction ; 

 then pause, from sixty to ninety seconds (in the case of 

 healthy plasmodia) ; then the current turns and streams 

 in the opposite direction. These streams sometimes unite 

 and sometimes divide. It is familiar that protoplasm when 

 enclosed in cells often exhibits movements, as in the well- 

 known case of the Chara, but then the movements are 

 naturally constrained by the cell walls ; in the free 

 protoplasm of the myxies no such restraint exists. 



If the peripheral edge of an advancing plasmodium be 

 examined, there will be found in advance of the granular 

 endoplasm a strip of the colourless and perfectly transparent 

 ectoplasm, of which we have already spoken ; it runs like 

 the foreshore along the coast of the body. Into this from 



