Tort] LUTMAN—CLOSTERIUM 4II 
to get a fairly complete series of stages of division in my whole 
mounts. Enough division figures were found in the sections, 
however, to assure me that the process was practically the same 
in the two species. 
External appearance of the division process 
FIscHER (14) has given a fairly complete description of the 
process of division as it can be seen both in the living specimens 
and in stained whole mounts, but in order to understand the 
structures and phenomena that are found in the sections it was 
necessary to restudy the whole process in detail, according to 
FiscHER’s method. It will be remembered, too, that owing to 
the density of the chromatophore and the granular nature of the 
cytoplasm, FiscHER was able only to guess at the nuclear changes 
that were occurring simultaneously with those seen in the cyto- — 
plasm. Further, it is practically impossible with whole mounts to 
discover the details of the method by which the new cross-wall is 
put across the old cell. 
Many species show parts of several generations in their cell 
walls. LirkKemMtLier (26) has made a careful study of a number 
of these species and genera. In both C. Ehrenbergii and C. moni- 
liferum, however, the process is a very simple one, and the wall, 
which is very thin and without markings, does not permit the 
distinction of the parts belonging to different cell generations. 
The first external appearance of division in an individual is a 
Pinching in of the chromatophore about a third of the distance from 
the middle to the tip (figs. 1-9). As previously noted, this occurs 
only in individuals that have their dark green chromatophores well 
filled with starch. This pinching in affects at first only the ridges 
of the chromatophore and occurs inside the plasma membrane, 
which becomes pulled away from the chromatophore. The 
mechanics of this process is difficult to understand. It is plain 
that the division of the chromatophore is entirely distinct from that 
of the cell. It has the appearance of being constricted as by a 
tubber band around it at this point. The division of the chroma- 
topore in Spirogyra and other Conjugatae is described as due to 
the constriction of the entire cell. The chromatophore here would 
