IN VEGETABLE BIOLOGY. 367 
This agrees exactly with Naegeli’s figure; but the gonidia 
do not always swarm within the zoosporangium at the same 
time; one may often find some in active movement, while others 
are still firmly fixed in position upon the wall, where they remaiu 
until long after the escape of their fellows. Under the most 
favourable circumstances the zoosporangium may be evacuated 
within half an bour of the first gonidium detaching itself from 
the wall; but much longer time is frequently taken, intervals 
sometimes of an hour or more recurring between the escape of two 
zoospores. The zoospore frees itself by gentle rocking from side to 
side, accompanied by a certain amount of movement about a 
vertical axis; as its deliverance approaches, somewhat violent 
swaying may sometimes be noticed, which would seem to indicate 
adhesion between the cilia and the zoosporangial wall, or at any 
rate the existence of some obstruetion to the indrawing of the 
cilia. Asan exceptional ease, swarming may occur when but few 
gonidia have been formed: on one occasion it was studied in an 
Apiocystis with only six gonidia; and fig. 16, Pl. LV., shows that 
at least one gonidium has escaped from a small individual which 
could not have had more than four gonidia. It will be noticed that 
the exit-aperture is in this case almost central, but a little nearer 
the base than the apex. Swarming zoospores were never seen to 
copulate within the zoosporangial cavity: hence my surmise of a 
few years back *, that Apiocystis and Chlorochytrium would even- 
tually prove closely allied forms, turns out an incorrect one. 
The liberated zoospores swim for about half an hour, when they 
settle upon a Cladophora-cell, lose their cilia and fix themselves 
by the colourless end; a new pair of cilia is formed distally, 
soon after the gonidium has secreted round itself a colourless wall. 
A second way by which the zoospores may escape is shown in 
figs. 9 a and b, Pl. LIV. Here, instead of the zoosporangial wall 
breaking down at one point, large portions of it may undergo 
degeneration before a single zoospore has succeeded in making 
its exit. In fig. 9a, while the proximal moiety retains its sharp 
contour, the distal portion has lost it, the wall here having been 
converted into gelatinous matter about which mention will be 
made directly. The boundary of this gelatinous matter is indicated 
in the figure by a faint line; but it is not so distinct in nature; 
indeed, the refractive index of this matter being so similar to 
* Journ. of Bot. 1884, p. 138. The gametangial nature of the Chlorochytrium 
zoosporangium was discovered by Klebs (Bot. Zeitung, 1881). 
