39 « 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
tentialities, the cell has acquired in the course of its evolution a suscepti¬ 
bility to differences in stimuli probably far beyond that possessed by any 
algal cell. This is another important feature in the evolution of complex 
organisms. 
The net result of the delicately adjusted responses to almost innumer¬ 
able stimuli—including particularly those due to the presence and activities 
of other cells in the same plant—is not only the orderly development of 
each cell but also a coordination in the development of all the cells. The 
coordinated responses of individual cells bring about “ regulated” growth 
and development. The totality of cellular development, thus coordinated, 
is called the life history of the organism. It is not surprising that some 
investigators, viewing the history of the organism as a whole rather than 
as made up of the histories of individual cells, and bewildered by the com¬ 
plexity of development thus considered, have expressed their despair by 
the coining of magic words or phrases, intended to express the inexpressible, 
to explain the inexplicable. This is a needless confession of hopelessness. 
It is reasonable, and immeasurably more profitable, to assume that regula¬ 
tion can be explained, by a painstaking analysis of the stimuli at work in 
ontogenetic development, of the potentialities whose expression is condi¬ 
tioned by these stimuli, and of the cellular organization out of which the 
potentialities arise. 
By means of such an analysis in terms of the individual cell, organic 
evolution must likewise ultimately be explained. Theories of the causes 
and of the course of evolution have been developed, in the main, in terms 
of the organism. All their sound elements can easily be restated in terms 
of the cell. Current discussions of evolutionary problems demonstrate 
that no material further progress is to be made by the use of the old terms 
and phrases. Consider, for example, the time and energy that are being 
wasted in controversies over the nature, the inheritance, and the modifi¬ 
cation of “ congenital ” and “ acquired ” characters, in which the characters 
are treated as qualities of the organism as a whole or of its constituent 
organs. There are no “characters ” of an organ, still less of an organism, 
save in a figurative or abstract sense. What concretely exists and is in¬ 
herited or modified from generation to generation is the fundamental con¬ 
stitution of the living matter, giving rise to certain potentialities and in 
some degree limiting and directing their expression. The organism is the 
resultant of the expression by each cell, under the conditions set by its con¬ 
stitution and by its environment, of some of its inherent potentialities. 
