190 DR. D. H. SCOTT ON NUCLEI 
seen, for example, in pollen mother-cells just before division. 
In some of the cells this fibrous body is broken up into a small 
number of portions. In all the latter cases indication of division 
of the cell by the ingrowth of a new transverse wall are found. 
In a few specially favourable examples indications of colourless 
strie, suggesting the idea of “achromatin fibres,” could be ob- 
served, connecting the portions of the nuclear structure, and 
iraversing the region when the new cell-wall was not yet com- 
plete. The small number of segments into which the chromatin 
thread breaks up suggests a comparison with such animal nuclei 
as that in the ovum of Ascaris. ` 
The other preparations shown, “Oscillaria No. 3” and Tolypo- 
thrix coactilis, were both prepared by the following method :— 
Treatment for two hours with picro-nigrosin solution was fol- 
lowed by immersion in saturated solution of chloral hydrate for 
two minutes, the filaments being subsequently mounted in pure 
glycerine. ” 
In “Oseillaria No. 3” the knot-like nuclei are very clear. 
Each nucleus is somewhat contracted, leaving a clear space 
between the chromatin thread and the general protoplasm of the 
cell. This phenomenon was long ago detected by Strasburger 
in the knot-stage of the nuclei of spore and pollen mother-cells. 
In this preparation division-stages are especially frequent, and far 
clearer than in “Oscillaria1.” The signs of achromatin fibres are 
more marked. It is hoped that the important subject of caryoki- 
nensis in these plants may be more fully dealt with in a future paper. 
It will clearly be of the greatest interest to know how far these 
phenomena show an agreement with those which are now so well 
known in the case of the higher plants. 
The Tolypothrix shows the same general characters, the slightiy 
contracted fibrous nuclei coming out with remarkable clearness. 
Here also some indications of division may be observed. 
It may be mentioned that other methods than those used for 
the preparations exhibited have been employed with similar 
results. It is unnecessary to go into these in detail. In all 
cases the same structure was shown, only slight differences in 
the amount of contraction of the nucleus being observed. In 
“Oscillaria 2," probably O. princeps, the nuclei are of an elliptical 
outline, and show the fibrous structure very plainly. 
The criticism which is most likely to be made on these observa- 
tions, and which has indeed been actually suggested by a distin- 
