464. IVAN E. WALLIN 
critics instead of further scientific analysis. Following Altmann’s 
dissertation, a great amount of theory has been advanced con- 
cerning mitochondria and cytoplasm. If we analyze many of 
these theories we find very little if any real evidence as a basis for 
their pronouncement. 
The cell may be considered a unit chemical factory into which 
materials are almost continually passing and products are being 
eliminated. The simplest type of cell, if it may be considered 
a cell, is the bacterial organism. It is simple in the sense that it 
responds more readily to environmental conditions than do the 
highly differentiated cells of complex organisms. Gourney- 
Dixon (’20) has collected a mass of evidence in this direction. 
During recent years there has been a great deal of evidence 
submitted to show that the cells of one tissue are dependent upon 
the product of the cells of other tissues. Adami (’10) even goes 
so far as to state that every cell in a complex organism performs 
the function of internal secretion. Such a relationship of cells 
is also present among the lowly bacteria and is designated as 
symbiosis by bacteriologists. This principle of cell dependence 
is, thus, not characteristic of the cells of higher organisms, but 
is a primitive adjustment. Further, it is highly probable that 
this principle of cell dependence has been a fundamental factor 
in organic evolution. 
The symbiotic bacterial conception of mitochondria, ap- 
parently, is not antagonistic to any known principles of cell 
activity. On the other hand, such a conception only extends 
the ‘cell dependence principle’ to include an intimate dependence 
of all highly organized cells on the activities of simple cells. The 
Bacillus radicicola in the root-nodules of Leguminosae is incon- 
trovertible testimony that such a functional and morphological 
relationship does exist. 
The dependence of higher life on bacteria in a different sense 
has been embodied into the biological conceptions of all students 
in biology. The principle of the ‘nitrogen cycle’ stands sponsor 
to these conceptions. It is within the domain of logic to extend 
this well-established principle of dependence of higher life on 
bacteria to include the more intimate dependence of life processes 
on bacteria. 
