Jan., 1922] NICHOLS — METHODS OF HEALING IN ALGAL CELLS 
25 
The formation of an internal membrane in the algae develops more 
slowly than the similar structure mentioned by Chambers, of which he 
writes : 
If a tear of the surface layer or of any part of the cytoplasm be so injurious that dis- 
organization sets in, a film may form around the disorganized area, separating it from the 
sound cytoplasm. The recovery of an injured cell is only brought about by the formation 
of a membrane-like film which prevents extension of the injury. A succession of films may 
form, as one after the other they succumb to the steady advance of the destroying process; 
and the film which finally holds out may enclose only a fraction of the original cell, but what 
it encloses will be normal protoplasm. 
In the algal cell it is impossible to feel that the new membrane cuts out 
all the injured contents, since the disturbance is very evidently felt through- 
out the cell, as shown by the moving particles and also by the fact that the 
protoplasm immediately within the new membrane appears as dense and 
disorganized as the portion cut off as a plug. Obviously this membrane 
cannot serve in checking the loss of protoplasm from the cell, as that move- 
ment has ceased some time previous to its formation. 
The presence of an enclosing wall is doubtless an important factor in 
developing various divergences from the responses of an ovum. One of 
the most essential of these is the readiness with which the loss of proto- 
plasm is checked by plugging the gap in the wall. Then, also, the wall 
ofifers an efifective support for the new membrane and new wall. 
The influence controlling the development and direction of growth of 
this new membrane may be similar to the stimuli acting in the case of spore 
formation as described by Harper ('99, '00) for Pilobolus and Fuligo. He 
found that 
There is no differentiation of hyaline zones or other special regions prior to the forma- 
tion of the cleavage furrows. Furthermore the nuclei show no special distribution about 
the cleavage planes. It is quite common to find a group of nuclei on one side of a cleavage 
furrow, while they are lacking over a considerable area on the opposite side. There is no 
indication whatever at this stage that the nuclei exert any direct influence on the orientation 
of the cleavage planes. 
If we examine the protoplasm immediately in front of these cleavage furrows also, we 
find it without differentiation of any sort which would indicate the direction which the 
furrow will take. 
After discussing the influence that the nuclei may exert on the later 
stages of spore formation, he states: 
On the other hand it is quite possible to assume that cleavage throughout is controlled 
by the cytoplasm, at first with little reference to the distribution of the nuclei, but later with 
special reference to the formation of uninucleated cells. 
In the separation of the plug, the cytoplasm appears to be the only 
controlling agent, for there is no visible movement of the nuclei toward 
the injured region. In the multinucleate forms discussed, a nucleus is 
found occasionally near the injury; but as nuclei are distributed throughout 
