1904] MERRIMAN: VEGETATIVE CELL DIVISION 189 
of the fusion of the chromosomes to form the spireme in the 
daughter nuclei, the spaces between the coils can be seen to be 
occupied by a diffusible and slightly stainable substance (figs. 
42-46). This substance becomes denser at last, resolving into 
the bodies which are known as the nucleoli of the resting nucleus. 
I think that this substance results from the mere deposition of 
particles coming from the disintegration of chromosomes into 
tetrad chromatin granules and the reduction of the latter in size. 
These particles, of a more or less plastic nature, increasing in pro- 
portion to the reduction of the chromatin granules, are entangled 
in the chromatic network only to be released with the dissolution 
of the nuclear membrane at the next mitosis. 
In connection with this view of the close relation of chromatin, 
linin, and nucleoli, it may be well to cite results of other investi- 
gators which accord in some measure with those secured in - 
Allium. 
In the case of Spirogyra, Meunier (4) and Mitzgewitsch (12) 
have claimed that during mitosis the nucleoli become converted 
into chromosomes and in the reconstructing daughter nuclei the 
chromosomes are transformed into nucleoli. Wisselingh (15) 
found that ten of the chromosomes arise from the nucleus, while 
the remaining two arise from the nucleolus. Hertwig (10) states 
in regard to the nuclear division of Actinosphaerium that the 
nucleoli may be classed as of two kinds, those containing chro- 
matic material and those free from chromatin. The latter he 
terms plastin nucleoli. They originate as small vesicles within 
the chromatin bridges. -His conclusion is the same as I reached 
in this investigation, namely that the material of the nucleoli was 
originally contained in the chromatin bridges. I would also add 
that in Allium the chromatin bridges are in turn derived from 
material originally contained in the chromosomes and result from 
their quantitative reduction. 
Since Strasburger (14) holds that the nucleoli of the higher 
plants are converted into the kinoplasm of the achromatic figure, 
he considers that the plastin nucleoli described by Hertwig are 
not at all analogous to those found in higher plants. 
Researches upon forms of the lower plants and animals indi- 
