THE POTENTIALITIES OF A CELL 1 
Charles E. Allen 
I 
On the basis of evidence now at hand, it is generally agreed that the 
flagellates represent the ancestral group from which came most existing 
plant and animal phyla. More specifically, it is to the free-living flagel¬ 
lates that we look, and, as concerns most groups of plants, to the pigmented 
forms, for the nearest contemporary approach to phylogenetic origins. 
It is not to be forgotten that the flagellates now living represent the out¬ 
come of as long an evolutionary development in point of time from any 
common point of departure as do the angiosperms; and that only very 
cautiously may conclusions be based upon present-day flagellates as to 
the nature of the forms from which higher organisms have been derived. 
With the latter fact in mind, however, certain suggestions of a very 
general nature seem fairly safe. 
One notable characteristic of the pigmented flagellates is a plasticity 
in form and function. The familiar Chlamydomonas, for example, may 
take the form of a flagellate cell; of an amoeboid cell which ingests organic 
food in an “animal-like” fashion; of a non-motile cell, divisions within 
whose wall result in the formation of a temporary colony; of a flagellate 
gamete; of a non-flagellate zygote, differing from the “vegetative.” quiescent 
form in the nature of its wall and of its secretions; and of a palmelloid 
colony. 
Myxochrisis paradoxa may be selected as another illustration. This 
brown flagellate, according to Pascher’s description, appears as cells, single 
or in small groups, with rigid walls, one-, two-, or several-nucleate; as 
naked, one-nucleate flagellate cells; as amoeboid cells; as filar plasmodia 
formed by the partial union of amoebae; as “true” plasmodia, resulting 
either from the growth of single amoebae accompanied by nuclear division, 
from a fusion of several of many amoebae or plasmodia, or from a com¬ 
bination of the two processes; and as encysted plasmodia which by division 
form temporary colonies. In each phase, some individuals lack the charac¬ 
teristic brown chromatophores. Cell division seems to occur in any phase 
except possibly the amoeboid. Different phases are characterized by holo- 
phytic or holozoic nutrition, or by a combination of the two methods. 
These instances appear to be fairly typical. Many species of both 
green and brown flagellates are described whose visible cellular organiza- 
1 Address of the retiring president of the Botanical Society of America, read at Boston, 
December 28, 1922. 
387 
