24 



PROTOPLASM AND THE CELL 



tion, is at present unknown. Such is the hypothesis as to the structure 

 of bioplasm which is probably the most accepted today among biologists 

 and cytologists. None the less, at the present stage in the development 

 of A human biological knowledge, the physical structure of protoplasm 

 involves many doubts and mysteries. 



Suppositions as to the Molecular Structure of Protoplasm. There have 

 been published one or two suppositions concerning the molecular or ultra- 

 visible structure of protoplasm which are worthy of repetition. They serve 

 to fix the imagination, thus giving it a useful basis to start with, a condition 

 much better than absolute vacuity. In lieu of the certain truth, a reason- 



FIG. 5 



Theories as to the physical structure of protoplasm. In the center is represented the structure 

 of a nucleus: 1, the granular theory; 2, the filament theory; 3, the foam (or vacuole) theory; 

 4, the reticular theory; 5, some of the crystals, etc., found in bioplasm at various times. 

 (H. K. Richardson.) 



able hypothesis is much better than nothing; "mere hypotheses" have 

 often established their high value to science. C. Nageli is the inventor 

 of the micellar theory of the ultimate structure of protoplasm. It is a sup- 

 position merely, but a pertinent one. As atoms combine to form mole- 

 cules, according to the atomic theory (long accepted, though never proved), 

 so Nageli imagines that in the case of living matter these molecules 

 unite in groups to form still more complex units, which he names micellae. 

 Each micella is supposed to be made of hundreds or of thousands of 

 molecules, although even then, large as the vital molecules surely are, 

 they are too small to be seen with any instrument now known, or even 

 with the ultraviolet rays. In protoplasm the micellse unite to form 



