Nuclear Division in Tetraspora lubrica. 
BY 
F. McAllister. 
School of Botany, University of Texas. 
With Plate LVI. 
I T is principally in those forms of animals and plants in which the nuclei 
are extremely minute, thus rendering the interpretation of the data 
uncertain — and in unicellular organisms or in those forms in which the cells 
are so isolated that great difficulty is experienced in finding numerous 
stages of nuclear division, — that mitosis is described as departing radically 
from the firmly established series of changes described for the higher 
organisms. Probably more different types of nuclear division have been 
reported for the protozoan cell than all others put together. 
To cite a few of the variations in mitosis reported for the protozoan 
cell — the nuclear material may not be collected in a nucleus, but is distri- 
buted throughout the protoplasm of the cell (Biitschli’s ‘ distributed nucleus ’), 
as is the case in Tetramites according to Calkins (4), and in Tracheloceroa 
according to Gruber (20) ; or the chromatic material may be collected in 
a nucleus but does not aggregate to form chromosomes — a fission of the 
chromatic granules occurring instead of a fission of chromosomes, as is the 
case in Euglena , according to Keuten (28) and others. In Noctiluca , 
according to Ishikawa (23, 24) and Calkins (5), chromatic bodies aggregate 
to form chromosomes. 
The origin of the spindle or its equivalent is also very variable 
according to the published accounts. A definite intranuclear spindle, with 
centrosphere-like bodies at the poles, is described for Etiglypha (Shewiakoff, 
43) as well as for other forms. In Euglena , according to Keuten (28), 
Dangeard (11), and others, an intranuclear body, the ‘ nucleo-centrosome ’, 
is made responsible for the division of the nucleus. This persistent body 
divides and the resulting halves move apart, though connected by an 
isthmus of the same material. The chromatic material groups about the 
two halves, and as they move apart the chromatin bodies pass to the poles 
with the ‘ nucleo-centrosome ’, and there organize new nuclei with the 
persistent body in the centre. 
[Annals of Botany, Vol. XXVII. No. CVIII. October, 1913.] 
