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MURIEL ROBERTSON. 
two dense chromatin-masses of the diaster-stage re-form into 
the two nuclei of the daughter-cells. The spireme is entirely 
suppressed at this point, and the reconstituted nuclei are, as 
has already been noted, of the reticulate type (figs. 22, 23). 
The young cells are narrower and project forward beyond the 
epithelium, and the nuclei appear for a time to be rather 
smaller than those of the neighbouring cells. The collar 
disintegrates at an early stage and is re-formed anew in each 
of the daughter-cells. It is interesting to note in passing 
that, although this is a quite typical metazoan mitosis, it reveals 
one or two rather primitive features, such as the very slight 
development of the spireme, the absence of rays from the 
centrosomes, and the general indistinctness of the chromosome. 
General Considerations. 
The main feature of interest in the foregoing account is that 
we have here another instance of a blepharoplast playing 
the part of centrosome, and the chief importance of the 
observation lies in the evidence it brings as to the simple 
achromatic nature of this structure. In a recent paper 
Hartmann and Chagas (1) describe the division of a number 
of free-living- flagellates, and some of the forms they deal 
with are of particular interest. 
The part of their work that bears most immediately on the 
question under consideration is that which treats of the 
division of Spongomonas uvella and Spongomonas 
splendida. Here two flagella are present in each individual, 
and there are two blepharoplasts which are generally not 
connected in any way with the nucleus and resemble in this 
particular the condition found in the collar-cells of Clath- 
rina coriacea. The authors are inclined to think that this 
is due to a secondary absorption of the rhizoplast, and is, as 
it were, a late condition in development. They are led to 
this conclusion by the fact that immediately after division 
the cells of Spongomonas show a quite clear connection 
between the blepharoplast and the karyosome of the nucleus. 
