THE PROrOPLASMIC SYSTEM 



of discrete drops of larger or smaller dimensions. They 

 give us no information concerning the mode in which the 

 living cytoplasm moulds the oil-drops — now coalescing 

 them, now emulsifying them. They fail to reveal the value 

 of such structure for life phenomena. Finally, for the 

 alveolar theory, a yolk-sphere is as much an "alveolus" as 

 an oil-drop; and yet although we do not know as much 

 about yolk as we would wish, nevertheless, what knowledge 

 we have is sufficient to warrant the conclusion that both 

 physically and chemically a yolk-sphere is something quite 

 different from an oil-drop; a yolk-sphere, unlike an oil-drop, 

 is a combination of fat and protein.^ If one adheres to the 

 alveolar theory by denominating oil-drops and yolk-spheres 

 "alveoli," one excludes from consideration the differences 

 between these "alveoli," thus stressing their shape rather 

 than their physico-chemical make-up. 



The filar theory of cytoplasmic structure never has 

 attracted many adherents, doubtless because of the limited 

 occurrence of fibrils in cytoplasm. For the most part, when 

 found, they are in fixed cells, in which, before fixation, they 

 can not be seen.^ The evidence for their presence in some 

 other living cells is by no means convincing. Thus, the 

 cytoplasm of outward flowing cell-processes appears to be 

 filar — but this may be due to granules disposed in rows by 

 the streaming of the medium that is forced through the 

 orifice.^ Mitochondria-granules may by close alignment 

 appear as fibrils. 



Altmann^ suggested that granules in the cytoplasm are 

 the elementary living substance. Both before and since 

 his time others have put forth similar theories, often includ- 

 ing more kinds of cellular granules than Altmann did. 



^ See also Konopacki^ 1929. 

 - Lewis and Lewis ^ ig24. 



3 See Biitschli, iSgo; also Just, igzSe. 



4 Altmann., iSgo. 



63 



