THE LIVING SUBSTANCE. 



1Z 



Biitschli as freely as in the water by peripheral protoplasm. As 

 soon as their structure is complete and their activities fully 

 organized, they function as if in a watery environment, and the 

 surrounding substance gives way before their rhythmic pressure 

 as a fluid alone would do. And when these structures are 

 from time to time returned by invagination to their native 

 environment, the protoplasm again yields fluidly to their beat. 

 It is after the manner of a visco-fluid that the living substance 

 yields also to pressure of adventitious substances, and to that 

 of internal filose activities along lines of the interalveolar foam, 

 as well as to pressure of contorted muscle bands.^ The change- 

 ful viscosity of the substance gives the necessary physical 

 opportunity for such phenomena. 



By such interalveolar activity are explained the seemingly 

 independent motions of the "granules," and many transposi- 

 tions of the nuclear elements. The motion of granules along, 

 and also to and from, pellicular surfaces Biitschli found himself 

 obliged to interpret by supposing the granules to be governed 

 by local surface tensions, and to have in this wise an independ- 

 ent motion of their own ; especially because these pellicular 

 surfaces bounded stable and seemingly motionless alveolar 

 layers of his special structure. This inference, although a 

 logical one if that structure be accepted as the final physical 

 structure of the living substance, can no longer be made in 

 view of the facts given here, which establish that such pellicles 

 are thick, and often compoundly viscid,«foam structures them- 

 selves, in whose area can be repeated the chief phenomena 

 characterizing the masses they as membranes limit. 



That cell walls have a value in protoplasmic masses of mere 

 areal arrangements of the finer foam is shown by countless 

 facts, some of which are to be given below. It is certain 

 that where cells are in close apposition, their walls become to 

 great extent common to both, or all, such cells. Granules and 

 even pigment, I have seen pass along the surface of adjacent 

 cells, with evident disregard of any separation line between 

 them as cells. Again, within the common mass of two fused 

 cells in egg cleavage, in that area which is central to the mass 



1 See Striation — formation of aster rays, etc. 



