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ultimate living units of structure. Wiesner has probably formu- 
lated the most plausible theory in regard to these ultimate units 
which he has designated plasomen. The plasomen, like Nageli’s 
micellz, have thus far only a hypothetical existence. The fol- 
lowing is a brief summary of Wiesner’s reasons for assuming the 
existence of plasomen. 
1. The more or less constant presence of organized individuals 
(nucleus, plastids, etc.) in the cell teaches conclusively that the 
cell cannot be the ultimate unit of living structures. 
2. Since all organized individuals of the cell originate from 
similar organized individuals, through division, it is to be sup- 
posed that all organized bodies found within the cell are not 
formed spontaneously but through fission. 
3. Mitosis teaches that the nucleus as well as cytoplasm con- 
sists of autodivisible organic individuals. From this we are in- 
duced to conclude that the nucleus and cytoplasm are not the ul- 
timate units of structure, but that ¢#ey are built up of ultimate 
units. The origin and development of the cell wall indicates that 
it is also made up of ultimate units. 
4. Autodivision within the cell goes beyond the limits of 
direct observation. A limit to the divisibility of living substance 
must exist. These last divisible living bodies of the cell are to be 
considered the ultimate units of structure (elementarorganismen). 
These ultimate units Wiesner designates plasomen. 
5. Plasomen have above all the power to divide, and since they 
divide continuously up to a certain limit they must also have the 
power to grow; but growth necessitates assimilation; hence 
divisibility, growth and assimilation are preéminently the propet- 
ties of plasomen. 
6. Organic cell individuals cues plastids, cell wall, derma- 
tosomen, etc.y are plasom aggregates. Cytoplasm is simply 2 — 
multitude of undifferentiated plasomen. 
7. Growth of cytoplasm, of cell wall, nuclei, plastids, takes 
place as does the growth of many-celled organisms; the latter 
grow as the result of cell growth and division, the former as the 
result of plasom division and growth. 
It is not my intention to discuss or explain Wiesner’s theory, 
but rather to give what I hold to be additional evidence as to the : ne 
