1192 Wisconsin Academy of Sciences, Arts and Letters . 
In connection with the normal cleavage of the cytoplasm cer¬ 
tain abnormalities in the manner of the formation of the second 
cleavage planes were described (37). In these abnormal cases 
the second cleavage planes are not formed at right angles to the 
primary cleavage plane, as is usually the case, but more or less 
parallel to the primary cleavage plane. When the daughter 
cells thus formed elongate and are liberated the colonies formed 
are similar to those shown in Figures 50 and 53. The extreme 
variation in cellular arrangement resulting from this abnormal 
cleavage is the rotation of one or two of the cells through an arc 
of 90 degrees so that the cells are in two different planes (Figs. 
42 & 43). 
Figure 60 is due to another type of abnormality in cleavage. 
Here there has been the usual first cleavage into two daughter 
cells, but in the second clevage of these cells there has been 
the failure to complete the cleavage in one of them. The be¬ 
ginning of this cleavage is shown in the notch at the top of the 
central cell. In the maturation of the cell, the elongation, and 
the formation of two pyrenoids has taken place in the usual 
manner. The nuclei of this cell were not seen but it seems 
likely that such a cell would possess two nuclei. Figures 61 
and 62 show three-celled coenobes in which one cell is much 
larger than the other two. Such abnormalities are probably duo 
to the complete inhibition of the second cleavage in one of the 
daughter cells. 
The liberation of the young colony from the mother cell wall 
is accomplished by the longitudinal splitting of the wall and 
the unrolling of the young colony. When the colony is first liber¬ 
ated the cells are not in one plane, as in normal mature coe- 
nobia, but in the form of a curved plate (Figs. 69, 73, 79, and 
81). Usually after the liberation there is a growth of the 
coenobe so that the cells form a flat plate. Some colonies do 
not become flattened but remain curved during their entire ex- 
istance. All gradations may be found in mature colonies be¬ 
tween a flattened plate and one that is markedly curved (Figs. 
86, 93-95). The cells of the colony are held together by a 
gelatinous material that forms the outer layer of the cell wall. 
