292 
R. A. HARPER 
Aside from this concentricity there is no evidence of symmetry relations 
or polarity in a polyphase colloidal system as such. On the other hand, 
polarity is one of the most obviously demonstrable characteristics of cell 
organization. Polarity in herbaceous and woody shoots is known to all. 
That the polarity of the shoot as a whole is due to the polarity of the indi- 
vidual cells has been made highly probable by appropriate experiments. 
That polarity is also a property of cells of simpler plants and doubtless of 
all cells is shown by Tobler's elaborate and far-reaching demonstrations 
for algal cells. 
The simplest possible statement of the facts as to polarity in the cell 
brings out at once the conspicuous differences between cell organization 
and that of a polyphase colloidal system as such. Greil, who is perhaps the 
latest to attack the problem from a theoretic standpoint, in his labored 
effort to bring all morphogenetic factors into an epigenetic rubric can get 
no further with the polarity of the animal egg than to say that it would be 
very remarkable if with such long-continued and mighty growth of the 
yolk-containing egg cell an entirely homogeneous consistency, tectonic, of 
the cell organization should be maintained. Polarity is for Greil simply a 
matter o eccentricity in the deposit of accumulated reserve materials, and 
yet this simple statement of its eccentricity at once differentiates the telo- 
lecithal yolk-bearing egg from a polyphase colloidal system as such. Greil 
quite ignores the fact that Tobler has shown the existence of pronounced 
polarity in algal cells which contain little or no reserve foodstuffs and that it 
has never been possible satisfactorily to associate the polarity of shoots, 
etc., of the higher plants with any special distribution of either "formative" 
or reserve stuffs. 
Greil goes so far as to say that the egg furnishes only bilateral polarity 
as a form-determining factor in the development of the embryo. This 
standpoint implies a program rather than present achievement, but it is 
interesting to us as showing what stress a confirmed epigeneticist like Greil 
lays on polarity as a characteristic of cell organization. To say that the 
egg furnishes only bilateral polarity as a form-determining factor implies 
that it will be possible to show how the bilateral polarity of the different 
species of eggs varies, since many eggs show bilateral polarity and yet with 
similar environment the product of their development is very different. 
It is not, of course, shown to be impossible that polarity may be in its 
essence simply the expression of the two-sided or bipolar distribution of 
the visible structural elements of the cell such as the nucleus, centrosome, 
plastids, etc. It would seem a priori more probable that the eccentricity 
in the deposit of such metaplasmic inclusions as yolk, starch, fat, aleurone, 
etc., is the expression of a polarity in the more fundamental architecture of 
the cell rather than its cause. This is the sort of polarity shown in Rabl's 
classic figure which represents in my opinion the most adequate diagram of 
cell organization so far conceived. The swarmspores of an alga like Pedias- 
