470 Harper. — Cell-Division in Sporangia and Asci. 
Berthold 1 describes the cleavage essentially as follows, 
basing his description chiefly on a study of the oogonia, and 
assuming that the processes in oogonium and sporangium 
are identical. The first step consists in differentiating a dense 
granular wall-layer around a central vacuole out of the, 
at first, more homogeneous protoplasmic contents of the 
oogonium. This layer of protoplasm then, at a certain 
definite number of centres, begins to form rounded pro- 
trusions into the central vacuole, the protoplasmic layer 
between these eminences becoming as a consequence thinner. 
These centres of aggregation become constantly larger, 
pushing out more and more into the central vacuole. The 
whole protoplasmic mass also contracts so as to be set fi'ee 
from the oogonial wall. Finally the different masses become 
entirely separated and round themselves up, though threads 
of protoplasm may connect them for a time after they have 
become well individualized. 
These balls of protoplasm now swell so as to become 
pressed together and flattened against each other, but 
ultimately round themselves up again and ripen into the 
mature oospores. 
From another point of view, the cleavage, according to 
Berthold. might be interpreted as proceeding from the central 
vacuole outward by means of very broad furrows which finally 
cut from the vacuole to and through the plasma membrane. 
No furrows from the surface inward are found. Berthold 
sums up the process for sporangium and oogonium under 
three heads : first, the separation of the contents of the spor- 
angium into a wall-layer and a central vacuole ; second, the 
loosing of this wall-layer from the cell-wall, and its division 
into a number of distinct heaps which finally separate entirely ; 
third, the forming of these masses into swarm-spores or 
eggs- 
Berthold’s object throughout is the explanation of the 
mechanics of the process. He regards the position of the 
spores as determined by a number of new centres of attraction 
1 Studien iiber Protoplasma-Mechanik, p. 308 : Leipzig, 1886. 
