366 MR. S. LE M. MOORE'8 STUDIES 
where there is no investing-wall, the gonidia lie either in one plane 
from the first, or the suecessive divisions are in three planes 
mutually at right angles; in this latter case, however, stretching 
of theinvesting-wall is usually followed by shifting of the gonidia 
into one plane. It is in this way that the numerous gonidia— 
about three hundredinthelargest of my specimens—are ultimately 
found to be ranged with more or less uniformity upon the parent 
wall. 
Apiocystis is usually more or less pyriform in shape ; but varia- 
tions from this form sometimes oceur. The small specimen shown 
in fig. 16, Pl. LV., is nearly cylindrical, and in fig. 15 is but shortly 
stalked: at fig. 6, Pl. LIV., is shown a rarely seen sessile variety ; 
and that of the succeeding figure is very remarkable, consisting of 
four pouches upon one stalk, each pouch with a number of closely 
massed gonidia: occasionally, too, the alga is rather ploughshare- 
shaped than pyriform. The stalk, especially when thin, is usually 
free from gonidia, except sometimes near the base, where a few 
may occur (fig. 11, Pl. LV). 
At the point of attachment to the Cladophora-cell there is 
almost always a brown discoloration visible from very early 
stages onwards. This would seem due to the presence of a 
substance, possibly of resinous nature, produced by the metabolic 
activity of the protoplasm of the zoospore. It appears, how- 
ever, to be insoluble both in chloroform and in carbon bisulphide. 
The suggestion has been made to me that this discoloration is the 
result of injury to the Cladophora-wall, which is, so to say, eaten 
into for a short distance by the Apiocystis ; but against this view 
may be urged the fact of the discoloured part projecting very 
frequently beyond the general surface. Sciadium, Hydrianum, 
Characium, and other fixed Alge have a similar discoloration at 
their point of attachment. 
After growth has continued for some time, the gonidia escape 
and swim about by meansof their cilia. "There are several ways 
in which this may happen: indeed, Apiocystis is chiefly remark- 
able for its polymorphism in this respect, and for the morpholo- 
gical interest accompanying some of these methods of zoospore- 
liberation. What is perhaps the most ordinary way is shown at 
fig. 8, where the gonidia are seen to be withdrawn from the wall 
of the zoosporangium, in the interior of which they are swarming 
with great activity: anaperture has made its appearance in the 
side ot the wall and through it a zoosporeis in the act of passing. 
