rgtt] LUTMAN—CLOSTERIUM : 417 
found in great numbers. This is especially important for the 
question here involved, as it is one of the critical stages in which 
the relation of the compound nucleolus to the spireme and the 
chromosomes should appear. 
As with mitosis in all plants, it is difficult to determine just the 
point at which the spireme starts to be differentiated out of the 
nuclear reticulum which gives rise to it. The reticulum seems 
to become drawn out into strands (fig. 19), but the exact method 
by which this takes place is not clear, for, as previously noted, the 
meshwork is a very delicate one, which stains very faintly and in 
which the structures are all very minute. These first strands, like 
the reticulum from which they are derived, apparently contain 
little chromatin in the form of granules (fig. 17), although a few 
such bodies are scattered in it; as the spireme grows more definite, 
however, there appear in it numerous small bodies which stain 
more densely (fig. 20). 
The compound nucleolus, in the meantime, retains its position 
at the center of the nucleus, but the partly fused masses that com- 
, Posed it now becomes separated into small spheres that are inde- 
Pendent of each other (figs. r9-23). This would seem to indicate 
that during the process of spireme formation, at least a portion 
of this central body is used. This body is suspended in the nuclear 
reticulum in some manner, but further than that it is not possible 
to see any connection between the two, such as has been shown for 
Aucleoli in some animal cells, and by WaGER (45) in the nuclei of 
the root tip of Phaseolus, in which he states that the nucleolus is 
teally only a very large granule or sphere on the linin thread. In 
the case of Closterium this central compound nucleolus apparently 
lies entirely clear of the reticulum, but this is undoubtedly only 
“pparent, as it would not retain its central position in the nucleolus 
if it were not attached. If part of the material forming this body 
does pass out to assist in forming the spireme thread, the passage 
Must occur while it is in a liquid state or as very small spheres. 
There is of course the possibility that the small, darker staining 
bodies on the spireme thread (fig. 20) may have migrated out in 
this manner, but the point to be particularly emphasized is that 
there is no passing out bodily of large pieces of this compound 
