iio Bristol. — Life-history and Cytology of Chlorochytrium grande. 
they have assumed an almost black colour. The action of a solution of 
chlor-zinc-iodine is to turn the inner layers of the wall an intense violet 
colour, while the outer layers remain unchanged. These two reactions show 
that the inner layers of the wall are composed of cellulose. To determine 
the nature of the outer layers a solution of cuprammonia was used. This 
reagent causes the inner cellulose layers to swell up, and finally to dissolve 
to form a mucilaginous mass completely filling the spaces in the cell pro- 
duced by the shrinking of the cytoplasm. If the material so treated is now 
washed with water and then with a 2 per cent, acetic acid solution, the 
addition of a solution of ammonium oxalate causes the slow dissolution of 
the outer layers of the wall, showing it to be composed of pectic substances. 1 
This conclusion is confirmed by staining sections of the cells with fuchsin, for 
the outer pectic layers acquire a deep pink colour while the inner cellulose 
layers remain colourless ; the fuchsin readily dissolves out of the pectic 
layers in alcohol. The cellulose layer varies in thickness from i to 4/x, 
while the pectic layer is rarely more than 1 /x thick in the vegetative cell. 
Cell-Contents. 
The cell-contents are granular and of a dense chlorophyll green, 
and, owing to the size of the cells and their intense colour, it is impos- 
sible to come to any conclusion as to their internal construction from an 
examination of the cell as a whole. It is possible, in a few ellipsoid cells, to 
differentiate between a central clear space and an intensely green peripheral 
portion (Fig. 1), but in spherical cells the chlorophyll entirely masks this, 
except in very early stages. The external surface of the cytoplasm appears 
in the living cell to be raised into very numerous, usually rounded lobes 
(Fig. 2), which give the cell-contents a somewhat mulberry-like appearance. 
From the centre of the cell a number of radiating lines can be seen on 
focusing to proceed towards the periphery of the cell, reaching the surface 
at the base of the depressions between the lobes. This appearance of the 
living cell led Borzi to conclude that the cell contains numerous rod-shaped 
chloroplasts, each with its base, either circular or angular by compression, 
closely applied to the inner surface of the cell-wall, and with a long 
cylindrical projection, which may be either straight or wavy, winding 
towards the centre of the cell, where there is a circular colourless area. 
The accuracy of this description of the chloroplast has been doubted on 
account of the difficulty of making correct observations in a cell of so large 
a size and so dense a colour, and the present work has done little to 
substantiate Borzi’s conclusions, for on one occasion only and in a single 
1 The action of the acetic acid in this case is to neutralize any ammonia which may remain, 
and to convert the pectic substances present into pectic acid, which is soluble in ammonium oxalate 
solution. 
