1166 Wisconsin Academy of Sciences, Arts, and Letters. 
Certain colonies may lose their symmetry either because of vari¬ 
ation in the position of certain individual cells, or because of 
the abnormal growth of certain cells. All such cases should 
really be classified with symmetrical forms, since each deviation 
is for a single generation only and the irregular coenobe gives 
rise in the next generation to symmetrical colonies. 
Classifying the arrangement of the cells in the coenobe ac¬ 
cording to the relationships of their long axes, we may divide 
colonies first into those the long axes of whose cells are all in a 
single plane (coplanar colonies) and those whose long axes are 
not in a plane (noncoplanar colonies). In the coplanar series 
the long axes may all meet at some one point, if they are pro¬ 
jected far enough, in which case they are called concurrent. 
cof/mcr 
non/wrtif/e/ 
Figure 2. Possible combinations of the four cells of a coenobe in a concurrent 
coplanar series. Shaded diagrams represent those arrangements which are 
known to exist in nature. 
Nonconcurrent coplanar colonies are those whose axes will not 
meet, no matter how far they are projected. The coplanar con¬ 
current forms may be further separated into those the long 
axes of whose cells lie in a single straight line (colinear), and 
those whose axes meet at a common center (nonparallel). No 
four-celled colonial forms are known with the coplanar concur¬ 
rent colinear arrangement of the major axes of the cells; but 
among the coplanar concurrent nonparallel forms may be men¬ 
tioned Pediasfrum Bormnum (Turp.) Mengh., Crucigenia tet- 
rapedia (Kirch.) W. & G. S. West, and Tet vast rum Staurogen- 
iae forme (Schroed.) Chodat. In coplanar nonconcurrent forms 
