236 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
have pointed out before, sufficiently obvious. It is also clear 
that no spatially differentiated representation of the organization 
of the colony in the organization of the mother cell could have 
any bearing on the method of transmission of the type configura- 
tion of the colony. In P. clathratum both the colonies and the 
cells are bilaterally symmetrical, both show polar differentiation, 
the colony in one axis and the cell in at least two axes, and yet the 
polarity and bilateral symmetry of the cell are in no sense repre- 
sentative of the polarity and bilateral symmetry of the colony. 
Neither predetermines the other directly though there can be no 
question here that the cells as independent units build the colony 
and their properties determine its properties. Surface tension is 
а common factor in determining the form of the cells and through 
the adhesion of the cells to each other in determining the rounded 
outline of the colony as a whole, but as I have already pointed out 
it is the inherited anomogenous consistency of the cells which is 
of most significance in determining their form and it is their 
motility, polar differentiations, and sensitiveness to pressure and 
contact stimuli which make it possible for them to achieve the 
highly symmetrical and characteristic interrelations shown in 
the pattern of the adult colony. I am discussing elsewhere (18) 
the possible relation of these contact and pressure interactions in 
the primitive ancestral cell group to the development of the form 
of the cells on the principle of functional hypertrophy. However 
it may be with this question, which involves the difficult problem 
of the inheritance of acquired characters, there can be no doubt 
that, as noted, in the species as one finds them the cell form 
in its major outlines is fixed by heredity and can be achieved by 
the cell when free and quite independent of pressure relations 
with other cells in the colony. That the typical cell form is 
developed to the extent that opportunity offers regardless of how 
the cell is placed in the colony is indicated by the perfection of the 
free lobe in one of the interior cells of the colony shown in FIGURE 
18 and by the development of a fairly good spine on one of the 
interior cells of the colony shown in FIGURE 4. More extended 
evidence on this point is presented in connection with my study 
of P. asperum (18). 
It seems to me, further, clear that the „ка polarity 
