146 
ALBERT H. TUTTLE 
The reticulum, which is never coarse or conspicuous, speedily 
passes over (fig. 5) into a well-defined spireme composed of a 
rather slender and greatl}^ contorted filament. Neither at this 
nor at any previous stage could a definite polarity^' be recog- 
nized. The nucleolus becomes still fainter, though not materially 
diminished in size. The spireme, which usually lies chiefly near 
the surface of the nucleus, soon breaks up into a large number of 
chromosomes, of varying size and great diversity of form (as 
Van Wisselingh has also shown), which are scattered irregularly 
throughout the nucleus (fig. 6). Quite a number of nuclei were 
found in which the spireme was more centrally situated, and 
others, apparently corresponding, in which the chromosomes were 
more or less centrally grouped. Fig. 7 is a well marked case of 
the latter. This centralizing of the spireme and of the newly 
formed chromosomes is possibly an artifact; but there was noth- 
ing in the appearance of the nuclei or of the cells in which it was 
observed to indicate that such is the case. By the time that the 
chromosomes are formed the nucleolus is very much reduced 
in size. It soon disappears altogether. 
By this time the nucleus has attained a magnitude and a shape 
which, while it undergoes some farther modification later in both 
respects, may conveniently be discussed here. While it is generally 
true that the nucleus undergoes some increase in size during the 
early stages of mitosis, the change in this respect in the nuclei of 
the vascular plants is insignificant when compared with that 
which takes place in (Edogonium. Any estimate of the latter 
must of course be only approximate. In making such an estimate 
a nucleus was chosen which was just approaching the metaphase, 
and whose form was that of a well-proportioned circular spindle : 
its length was a little over 32/i; its transverse diameter was 16m. 
All the resting nuclei in the same fragment of the filament were 
approximately spherical in form, with an average diameter of 
12iu. The computed volumes of such a spindle and such a sphere 
are to each other approximately as 4.4 to 1 (corresponding closely 
to that of two spheres whose diameters are to each other as 20 
to 12): the superficial areas of the spindle and the sphere in 
question are to each other approximately as 2| to 1. 
