430 Griffiths.—On Glaucocystis Nostochinearum , Itzigsohn. 
shows a distinct tendency to be independent of the division of the karyo- 
plasm. (3) Phycocyanin is present as the colouring substance. 
It differs from most Cyanophyceae in the following particulars : 
(1) The nucleus preparatory to division becomes ‘closed \ It has a mem¬ 
brane and a nuclear reticulum possessing chromatin. The chromatin is 
aggregated into a single mass which divides by transverse fission. (2) After 
division of the cytoplasm, the two parts become rounded off and daughter- 
cells are formed, very similar to those of Oocystis. (3) The cell-wall 
consists very largely of cellulose. (4) There is a definite and elaborate 
chromoplast. 
Summary. 
Glaucocystis Nostochinearum, Itzigsohn, is a unicellular solitary alga 
found generally in Sphagnum-bogs . It is ellipsoidal, and measures from 
30 to 45 [jl in length, and from 18 to 25/x in breadth. It has a small 
internal polar thickening of the cell-wall at each end, and an equatorial 
external thickening. The cell-wall is composed mainly of cellulose. There 
is a definite chromoplast consisting of a number of strongly recurved and 
radiating bands of a blue-green colour. These break up into numerous short 
pieces in the division stage of the cell. The organism reproduces by the 
formation of two, four, or eight daughter-cells lying freely within the 
mother-cell wall. 
In the resting stage the nucleus is of the ‘ open ’ type. It consists of 
a large colourless spherical portion of the delicate reticulate protoplasm, 
and is practically unstainable. It is only distinguished from the general 
cytoplasm by the complete absence of the metachromatin granules. This 
portion lies close against the cell-wall. 
In the division stage, the nuclear portion of the protoplasm contracts, 
becomes coarsely reticulate, moves to the centre of the cell, and becomes 
stainable. Chromatin develops in this reticulum, and a nuclear membrane 
forms. The metachromatin granules of the cytoplasm gradually disappear. 
The chromatin of the nucleus aggregates into a large karyosome. This 
divides by transverse fission, and each part rounds off. The cytoplasm 
divides by transverse fission, each half rounds off, and daughter-cell walls 
are formed. 
Glaucocystis is probably a member of the Cyanophyceae owing to the 
presence of an ‘ open 5 nucleus at one stage ; the tendency of cytoplasmic 
division to take place independently of nuclear division; and to the presence 
of phycocyanin in the chromoplast. The very high differentiation of the 
nucleus in the dividing stage ; the elaborate chromoplast to which the 
phycocyanin is confined; the formation of daughter-cells very similar to 
those of Oocystis ; and the cellulose character of the cell-wall, are features 
