Bristol . — Life-history dud Cytology of Chlorochytrmm grande. 1 1 1 
individual has a chloroplast of this description been observed (Fig. 3), 
though several thousands of individuals must have been examined. The 
appearance in this case was probably due to vacuolation of the cytoplasm, 
since the material in which it was found was attacked by a fungus and many 
of the other cells were abnormal in various ways. 
An attempt has therefore been made to determine the exact nature 
of the chloroplast by means of stained microtome sections of the alga of 
thicknesses varying from 4 to 8 /x. Different fixing reagents were used, 
including 
i. Corrosive sublimate. 3 per cent, solution in 50 per cent, alcohol, 
containing 3 per cent, of glacial acetic acid. 
ii. Absolute alcohol 3 vols. with glacial acetic acid 1 vol. 
iii. Bouin’s solution containing 
Concentrated aqueous picric acid . . 15 parts 
30 per cent, solution of formalin . . 5 parts 
Glacial acetic acid .... 1 part. 
The stains used were Delafield’s haematoxylin, acid fuchsin-iodine-green, 
and Heidenhain’s iron-alum-haematoxylin, the best results being obtained 
by fixing with Bouin’s solution for twenty minutes and staining with 
Heidenhain’s haematoxylin. 
Sections prepared in this way show the presence of a large nucleus in 
a more or less central position, and a peripheral cytoplasm containing 
a deeply staining, coarse, granular reticulum, especially thickened at the 
angles of the network. The spaces within the reticulum are filled by a 
small-meshed, faintly staining network containing a number of small 
granules. The pattern of the coarse reticulum varies according to the part 
of the cell through which the section passes. In a median section (Figs. 4- 
6) the reticulum is seen to take the form of more or less regular rays which 
branch towards the periphery and are connected up in various planes 
with other similar rays. The deeply staining reticulations enlarge slightly 
at the outside and seem to be connected together by a thin, deeply 
staining layer surrounding the whole of the cytoplasm. In a few cases 
only in the stained preparations was there any trace of the apparent 
lobed structure of the surface of the cytoplasm so characteristic of the 
living cells. 
In a more tangential section (Fig. 7) the reticulum forms a network 
enclosing more or less polygonal spaces of varying sizes and shapes. 
These are transverse or somewhat oblique sections of the rays seen in 
the median sections, and their irregularity is due not only to the vary- 
ing sizes of the rays, but also to the fusion of adjacent rays. Sections 
taken through the extreme periphery of the cell show a very character- 
istic appearance (Fig. 8). The deeply staining reticulations are very much 
