6 A. \V. GREELEY. 



on the condition of its constituent particles. It is significant to 

 find, that all the controversies that have been waged over the 

 various theories of a fixed morphological structure in protoplasm 

 have centered about the supposed unchanging physical condition 

 of these more solid or viscous elements in the protoplasm. Now 

 in the artificial colloids we see that their physical state varies di- 

 rectly with certain external conditions. The protoplasmic particles 

 of course are vastly larger than the particles in an artificial colloidal 

 solution, and we have no right to assume that the two are identical. 

 But the protoplasmic granules bear the same relation to the cell- 

 sap as the colloidal particles do to the fluid matrix, and they 

 both respond to chemical and physical changes in a similar man- 

 ner. A close comparison of the behavior of these two structural 

 elements under various conditions will, I believe, throw a great 

 deal of light on the physical basis of protoplasm. 



Hardy observed that when a colloidal solution is exposed to 

 the action of certain so-called fixing agents, the same structures 

 are produced as by the action of these fixing agents upon proto- 

 plasm, viz.: a coagulation occurs in which the colloidal particles 

 fuse in definite ways, producing a type of structure varying with 

 the fixing agent employed. He therefore concluded that coagu- 

 lation of the protoplasm is necessary to reveal the fixed types of 

 structure thought by some to be characteristic of protoplasm 

 under all conditions. Such types of structure then appeared to 

 be in protoplasm, as in the organic colloids, merely artefacts ; 

 and Hardy argued that protoplasm in the living condition must 

 be identical, as far as its physical structure is concerned, with the 

 organic colloids in the " sol " phase, and that like the colloids 

 its structure is constantly changing with the external conditions. 

 Undoubtedly under the same external conditions, the protoplasm 

 of different forms will show varying types of structure, as the above 

 statement will allow. In some cases this structure may resemble 

 a reticulum or other types described by the morphologists, but 

 no one will now maintain that such a type is of universal occur- 

 rence. In the living protoplasm of Paramoscium, I have never 

 .seen a trace of a fixed structure. 



These suggestions of Hardy and others upon the physical 

 structure of protoplasm remained almost unnoticed by biolo- 



