254 PROTOPLASM 



(j) Striated Protoplasm of Epithelial Cells 



That the radiate appearances are not always caused by the 

 central body seems to me further to follow from the fact 

 that there is no sharp distinction between them and the 

 striated appearances which epithelial cells exhibit so often, 

 perhaps even universally. Both depend, as I have already 

 explained before, upon the same cause, i.e. upon a regular 

 arrangement of the alveoli. Now this arrangement of the 

 alveoli in parallel rows has no relation either to the nucleus 

 or to any central body that may be present, but it always 

 runs parallel to an axis of the cell, which is directed 

 vertically to its outer surface. Since, however, there is no 

 obvious reason for regarding the striated structure of the 

 alveolar framework of these cells as a consequence of strain 

 or tension in the direction of the striation, since the same 

 striation is shown also by cells which are shorter in the 

 direction of the axis than in one at right angles to it, and 

 the fibrous appearance sometimes does not extend through 

 the whole cell, it may be assumed that in these cases the 

 longitudinal striation depends in the same manner as a 

 rule upon diffusion currents. The fact that such diffusion 

 currents are usually present in epithelial cells and 

 especially in gland cells, and that then they must take the 

 direction indicated by the longitudinal striation, scarcely 

 requires any further elucidation, whether these currents 

 move towards the exterior or towards the interior of the cell. 

 As has been said, I therefore consider it most probable that 

 the striation of the epithelial cells depends in general upon 

 the same cause as the appearance of radial striation. 



On the other hand, there are a large number of cases 

 in which protoplasm exhibits striated alveolar structures, 



chelmis, is to tie included here, remains an open question, inasmuch as a 

 central body is certainly present in the vicinity of the germinal vesicle. If, 

 however, the rays are regularly centred round the germinal vesicle as 

 Vejdowsky alleges, I consider it certain that they are produced by it. There 

 is no inherent difficulty in supposing that at one time the nucleus, at auother 

 time the central body, may be the cause of radiating appearances, or that 

 occasionally both may manifest at the same time an activity of this kind. 



