Harper . — Cell-Division in Sporangia and Asci . 495 
is seen to be analogous to the process in the growth of a 
pseudopod on an Amoeba , and the same distinction of central 
outflowing currents and slight peripheral backward currents 
can be observed. Noll has already pointed out that the 
growth of a coenocytic alga like Caiderpa is to be compared 
to the creeping of an Amoeba , and the comparison is equally 
striking here. 
The central portion of the young sporangium is largely 
filled with cell-sap, only a few strands of protoplasm cutting 
through it. Outside this central area the protoplasm is 
spongy and thready, becoming denser toward the periphery. 
The outer layer is dense and quite homogeneous from the 
start, and is slightly thinner at the apex of the sporangium. 
The appearances in these young sporangia are suggestive with 
reference to the question as to the gross structure of proto- 
plasm. In Figure 11 for example the plasma is not vacuo- 
lated in the ordinary sense, though an immense amount of 
cell-sap is present. This sap is not contained in more or less 
rounded cavities like the vacuoles as commonly described. 
The protoplasm forms rather a spongy framework in whose 
meshes is the cell-sap, The whole mass of sap occupies the 
interstices of the plasma-net, and is not divided off in isolated 
vacuoles. The sap is a continuum , in which the plasma- 
strands float as a net or framework. Later, after the upward 
flow is complete, the plasma passes into a truly vacuolated 
condition, when the cell-sap is contained in rounded cavities 
whose outlines are determined by surface tension. A similar 
transition from a foamy vacuolated structure to a spongy 
structure will be described later in the account of the ger- 
mination of the spores. The whole sporangium continues to 
grow in size for a considerable period (5 p.m. until about mid- 
night), and its wall in the apical region becomes thickened 
and dark coloured. The layer of spore-plasma becomes 
thicker by the increase in density of the spongy plasma on 
its inner surface. The circular ridge becomes higher, and to 
the outside, between it and the spore plasma, an open spongy 
mass is maintained which already indicates the outline of the 
