Ig1r] LUTMAN—CLOSTERIUM 405 
and its substance having been used up probably in the formation 
of this spireme. After metaphase the chromosomes form two new 
spiremes, one at either pole, in the midst of which the nucleoli 
reappear. In 1884, in Spirogyra nitida, STRASBURGER (38) observed 
that the spireme appeared close to the nucleolus, which as a result 
seemed to take on a granular corroded appearance. In his paper 
in 1888 (39) he finds that in Spirogyra polytaeniata a typical 
spireme, gradually becoming denser, is formed in the nuclear 
reticulum, while the nucleolus disappears about the end of its 
formation. Twelve chromosomes are formed, which during the 
telophase form new spiremes and become reticulated. In other 
words, at this time in this species of Spirogyra, STRASBURGER 
believed that the nucleoli do not behave very differently in mitosis 
from those of higher plants. ; 
FiemMING (16) considered the spireme to be formed partly 
from the material in the nucleolus which became arranged in it. 
The achromatic part of the reticulum is utilized in the formation 
of the spindle. Tancr (41) claimed that the equatorial plate 
arose directly from the nucleolus, while CarNnoy (6) believed that 
all the chromatic material in the nucleus was collected in the 
nucleolus, forming there a still smaller body which he proposed 
calling the nucleo-nucleolus. The nuclear cavity surrounding this 
body was empty. MEuNIER (30) confirmed these observations, 
finding a spireme formed inside the nucleolus in the early prophases. 
In the reconstruction stages the achromatic basis of the nucleolus 
is established first, and. then on this the chromatic substance is 
deposited. 
ZAcHARIAS (48), as a result of microchemical tests, considered 
the nucleolus as pure plastin and similar to that of the higher 
plants. 
Decacny (7) in 1890 believed that while there was chromatin 
both in the nucleolus and in the extra-nucleolar part of the nucleus, 
it was the nucleolus alone that formed the plate. In later papers, 
however, he changed this opinion, and derived the plate from the 
spireme which comes to envelop the nucleolus closely and seems 
to absorb the substance from it. 
Both Mott (32) and MrrzkewrrcH (31), applying modern 
