142 Trow . — Observations on the Biology and 
observation. The commencement of oosphere-formation was 
noted at 12.40 p.m., two hours later, and continuous obser- 
vations were made up to 4.45 p.m., when the fertilization- 
tubes had been lost to sight for some time behind the eggs — 
now presumably fertilized. Figs. 10 to 18 illustrate fully 
how the eggs are produced and the time occupied by each 
stage in development. It may be noted how the protoplasm 
heaps itself around certain centres, causing a thinning out 
over the intervening areas ; how the oil-globules flow into 
the heaps thus produced, and project from their surfaces, 
leaving behind them a clear thin film of protoplasm ; how 
when this film is ruptured the separate masses of protoplasm 
swell up ; how they contract again, rounding themselves off 
until they appear an hour and a half after the first indication 
of their formation as perfectly spherical bodies densely filled 
with oil-globules and having a smooth external layer of 
hyaloplasm ; and finally, how the fertilization-tubes grow out 
and place themselves in contact with the naked oospheres. 
Neither in this case nor in that of many others examined 
have I been able to trace the entry of the fertilization-tube 
into the egg; it appears to grow past it, and on the side 
furthest removed from observation, possibly influenced thereto 
by the illumination from below. Protoplasm containing fine 
granules may be observed to pass slowly along the fertili- 
zation-tube, but I have never detected any rapid movement 
such as some observers insist must take place during ferti- 
lization. 
Maturation of the oospores . The oospheres, after contact 
with the fertilization-tubes, surround themselves with a thin 
cell-wall, which gradually gets thicker and is apparently 
differentiated into an exosporium and endosporium. As 
development proceeds the oil-globules coalesce, until finally 
they form a single large eccentric one situated outside the 
protoplasm. A second wall is produced inside the first one, 
and this curiously enough appears to be separated from the 
outer one by a clear space — an optical delusion, as the study 
of sections proves. Each wall, outer and inner, is of consider- 
