242 



PROTOPLASM 



of a vacuolar structure (Fig. 116). This may be true, but as 

 vacuoles, like alveoli, are droplets of liquid, we can say that all 

 forms of the microscopically visible structure of protoplasm are 

 modifications of an emulsion. 



Fig. 119. — Quiescent protoplasm 

 (slime mold) as seen through the 

 Spierer lens. 



Fig. 120.— Sketch 

 of a plant-cell nucleus 

 as seen through the 

 Spierer lens. 



Protoplasm, as Butschli contended, is usually if not always of 

 a very fine emulsion structure, even though such a structure is 

 not visible with ordinary optical methods. That this is true is 

 indicated by the following observation. Protoplasm, which 

 appears to be a homogeneous, hyaline substance, free of granules, 





a 



Fig. 121. — ^Representation of protoplasm as seen through the Spierer lens; (a) 



streaming; (6) as a thread. 



may be revealed as a very fine emulsion when viewed with the 

 Spierer lens (page 98). The one (dispersed) phase of the 

 emulsion is brightly illuminated, while the other (dispersion 

 medium) remains dark. When the protoplasm is quiet, the two 

 phases present a mottled picture, a mosaic (Fig. 119). The 

 plant-cell nucleus is of a similar appearance (Fig. 120) ; here the 

 structure is often visible with ordinary (direct) illumination. 



