14 
Olive, Mitotic division of tlie liuclei of tlie Cyanopliyceae. 
tlie present paper. Botli are cross sections of Oscillatoria prin- 
ceps, drawn with carnera to about tlie same scale. Both are 
stained witli iron baematoxylin and show much tlie same featnres. 
It will be noticed, böwever, that tlie vacuoles in Bis eher’ s figure 
are drawn perfectly ronnd instead of angular and tlie ebromatin 
granules are relatively too small, facts wbicb I liave supposed 
might be attributable to tlie carelessness of tlie litliograplier 
to wbom tlie making of tlie drawings was intrusted. It is truly 
remarkable, howeVer, tliat Bischer did not at least attempt to 
give an explanation of tlie niinute black granules sliown in this 
figure as well as in figure 37, other than simply to call them 
„Granulationen“. Even a casual glance will sliow tliat they are 
not tlie same as tlie relatively much langer granules of liis 
hgure 41b, e. g., or, indeed, of any of liis ligures of granulär 
inclusions. How tlie fact tliat tlie niinute granules sliown in 
figure 36 stain exactly as do tlie chromatin granules and tliat 
they have in addition other characteristics which belong to the 
chromatin. of nuclei, could have escaped so noted an observer 
as Bischer, is to the writer inexplicable. 
Wäger, in his recent preliminary paper, sliows apparently 
only one figure which is drawn from a section, and, in tlie 
opinion of tlie writer, this cross section was probably strongly 
overstained. At any rate, in my own iron haematoxylin prepa- 
rations, I can find many similar appear, ances, resulting from a 
failure to wash out sufficiently. In fact I have seen, in my 
own preparations, satisfactory explanations for such misleading 
appearances as are sliown by Wäger in his figure 1, which 
lead him to tlie conclusion tliat the division of the nucleus is 
direct. And, moreover, in thick, deeply stained sections, one 
may find similar figures to t.hose given by Kohl — ligures 
10 —12, and 16, of Plate e; 14 and 15 of Plate f; and the most 
of the figures of Plates i and k, — to prove the opposite con¬ 
clusion that the division of the nucleus is indirect. It is easy 
to find, in overstained or badly hxed mounts, such long streaks 
of blended chromatic and fibrous achromatic elements (see 
figs. 2, 3) as are sliown by the figures of botli Wäger and 
Kohl, and which are interpreted by the latter as the eliromo- 
somes of a mitotic figure, and by Wäger as the chromatin 
granules of a simple amitotic division. Overstained or poorly 
hxed preparations and attempts to fatliom from without instead 
of examining from thin sections the internal structure of a cell 
which contains at least three different kinds of granulär in- 
clusions and a protoplasmic structure showing considerable 
amount of differentiation, must be held in the main responsible 
for the extreme confusion and conflicting results witli which we 
are confronted. 
Tlie coloring* matters, 
As was first pointed out by Schmitz, in 1879, a close 
examination of one of the blue green algae reveals the fact 
that, even in the living condition, we may distinguisli two 
