MITOSIS IN (EDOGONILM 
145 
I wish to acknowledge my obligations to my colleague and for- 
mer student, Dr. Wm. A. Kepner, who has kindly made the draw- 
ings with which this paper is illustrated; he has also gone over the 
material with me step by step and confirmed or checked my obser- 
vations. While I alone am to be held responsible for any state- 
ment or conclusions presented, I am indebted to Dr. Kepner for 
many observations and suggestions. 
The nucleus of the species studied, when in the resting phase, 
is quite uniform in size and shape, however much the dimensions 
of the containing cells may vary. It is almost always approxi- 
mately spherical (fig. 1), its outline being apparently circular, 
whether seen as there figured or in a position at right angles to 
this as in fig. 2, or in a transverse section; occasionally there is 
some slight distortion, as in fig. 2, but in such case there is no 
constancy in the direction of the enlargement. Of the hundreds 
of resting nuclei which I have examined (both in living and in 
preserved material), I have not found one which could properly be 
called an oblate spheroid. The diameter is approximately twelve 
micra, rarely more than thirteen. There is a single large and well 
defined nucleolus. The chromatin is present in the form of nu- 
merous distinct granules of varying size. 
The process of mitosis goes on concurrently with the peculiar 
formation and modification of the ''ring'' which precedes the 
elongation of the cell wall. Wherever a ring can be detected upon 
a cell the nucleus will be found to be in one or another mitotic 
phase; and such phases are never found until the formation of 
the ring has begun. These facts are of great service in searching 
for nuclei undergoing division, either in living or in preserved 
material. 
The first change (fig. 3) is a marked enlargement of the nucleus 
with a distinct elongation parallel to the axis of the cell: the 
nucleolus is still conspicuous, and the chromatin is still distrib- 
uted in granules. This is followed by still greater elongation 
and the assumption (fig. 4) of a characteristic fusiform shape: the 
nucleolus is paler; and traces now appear of a reticular arrange- 
ment of the chromatin, nothing of which was discovered at an 
earlier stage. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 9, NO. 1. 
