28 ANDREWS. 



area can be foretold by just these characteristic differences, 

 which are identical with those seen in most ectosarcal areas 

 and products. 



It is by local differences in viscosity that differences of shape 

 in masses, which had their origin in protoplasmic activities, 

 are maintained, until they may or may not be released to pass 

 into physical control of secreted, or adventitious, non-living 

 materials. The same is true of those internal cavities, or 

 vesicles, whose complex, non-spherical forms have been used 

 as an argument against Biitschli's foam theory. 



Variations in viscidity of the substance as masses, or areas, 

 are optically manifest as differences in the same manner as 

 shown for pellicular substance. 



Increased viscidity does not always mean structural subdi- 

 vision of Biitschli's structure, although this of itself is physi- 

 cally a common cause of increased viscidity {ceteris paribus) 

 wherever it occurs. 



Nor does it necessarily mean in living foams, as it usually 

 does in physical foams, an increased tenuity of the lamellar 

 membranes of Biitschli's or other visible structure. 



In living foams, the structure of a given area of great 

 viscidity may be in size not at all different from surrounding 

 areas ; yet the viscidity shown under pressure, or osmotic con- 

 ditions, may be far above that of these latter. 



The continuous substance may be no thinner, may even be 

 markedly thicker, than that of the adjacent protoplasm, and yet 

 the areal viscidity vastly greater. 



Hence comes it, that there is often found an areal viscidity 

 which may have almost any structural character in point of size 

 of alveoli, or distribution of the continuous element of a given 

 structure. 



All such states and conditions may be seen freely inter- 

 changed and playing freely into each other in the protoplast, 

 Amceba radiosa ; coarse and fluid structure changing in a 

 moment's time into minute and highly refractive areas ; 

 these returning to coarse and highly viscid states ; these 

 again to finely subdivided states, which may be either fluid 

 or viscid. 



