406 BOTANICAL GAZETTE [JUNE 
cytological technic and using microtome sections, arrived at the 
conclusion that practically all the chromatin was centered in the 
nucleolus. Mott found the chromatin coming out of the nucleolus, 
leaving the latter empty. This chromatin then formed a spireme 
which cut up into 12 chromosomes. MITZKEWITCH found in the 
nucleolus two constituents, chromatin and linin. The chromatin 
appeared in the early prophases of division in the form of a definite 
number (24) of bodies imbedded in a mass of more lightly staining 
linin. This mass occupies the position formerly held by the 
nucleolus, and apparently seems to have resulted from its trans- 
formation. 
VAN WISSELINGH (42, 43, 44), by a process of progressive diges- 
tion of the various parts of the nucleus by 40 per cent chromic acid, 
came to the conclusion that the nucleolus contains chromatin. 
He also found chromatin in the surrounding reticulum. He 
ascribed the origin of only two of the chromosomes to the nucleoli; 
if there are two nucleoli one chromosome comes from each; the 
other ten arise from the nuclear reticulum. __ 
BeErGus (2) has recently devoted a very long paper to a detailed 
account of the process as he finds it in a Spirogyra which he believes 
to be S. nitida. He finds all of the 12 chromosomes arising from 
the nucleolus, the reticulum surrounding it being entirely free from 
chromatin. After the chromosomes are formed, there still remains 
in the nucleolus a second substance which stains less deeply. This 
substance divides transversely into two groups of pieces which 
move to the poles with the chromosomes, The nucleus is recon- 
structed out of these two substances, which, after undergoing 
vacuolization, are condensed in the nucleolus. 
KarsTEN (25) finds in the first division of the fusion nucleus 
in the zygospore of Spirogyra jugalis that 14 tetrads arise from the 
nucleolus, which lies surrounded by light plasma containing two 
or more weakly staining chromatin spheres, apparently comparable 
to the extruded nucleoli of other plants. He has followed the 
development of these chromosomes and finds them appearing 
gradually in the dark stained nucleolar mass. This stage he believes 
to be comparable to synapsis in the higher plants. 
Miss MERRIMAN (29) finds in Zygnema a central body which 
