246 PROTOPLASM 



The reticular, fibrillar, net, and spongelike structures seen in 

 fixed protoplasm may be true fibrous coagula or pictures of an 

 emulsion caught in a coagulum; for example, "chromatin 

 granules" on a "linin thread," a structure that has played a 

 prominent role in modern cytological and genetical theories of 

 nuclear behavior, is readily reproduced by a distorted emulsion 

 of large globules with a minimum of dispersion medium. The 

 granules would then be the interstices where several globules 

 approach each other, and the linin thread would be the connecting 

 strands of the dispersion medium. This is shown by comparing 

 a typical drawing of chromatin material (Fig. 125) showing 



Fig. 125. — A typical cytological picture of "chromatin granules" on a "linin 

 thread." (Compare with C, D, and E, Fig. 150.) {From C. J. Chamberlain.) 



chromatin granules on a linin thread, with one or more of the 

 possible configurations of an emulsion (particularly E, Fig. 118). 

 The symmetrical arrangement of the phases of an emulsion 

 might well pass for the picture of a net or reticulum. 



With the older concept of a framework as the structural basis 

 of protoplasm in mind, but with the realization that the earlier 

 evidence for it is not always sound, let us turn to modern 

 theories. 



THE ULTRAMICROSCOPIC STRUCTURE OF PROTOPLASM 



The ultramicroscopic structure of protoplasm, like that of 

 nonliving matter, is obviously not visible, but theories per- 

 taining to it, like those of molecular and atomic structure, are 

 based on sound though indirect evidence. We can best approach 

 our problem by a simple analogy. Of two soap solutions, one 

 of low concentration and low viscosity and one of high concen- 



