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William J. Hodgetts. 
of the gametangium (or apex of the protuberance), since the 
actual wall of the protuberance here is usually much swollen and 
more or less mucilaginous at this stage. At the other end of the 
gametangium, however, the inner membrane is not always clearly 
marked off from the septum which cut off the gametangium; in 
fact the two, being generally in such close relation to each other, 
often appear as a single wall, but they may be separated, and in 
the zygospore stage (see below) readily come apart. Thus, prior 
to fusion of the gametes , each of the latter is surrounded by a 
double investment, a state of affairs which appears—as far as is 
known at present—to be unique amongst the Conjugatse. 
In Pig. 1, C (drawn from a specimen mounted in glycerine 
jelly) the two gametangia have been torn apart in the mounting, 
and the inner wall (a) round each gamete is well shown. This 
might have been interpreted as being the development of twin 
spores ( i.e ., two azygospores), but since all possible degrees of 
fusion between these double-walled gametes were observed, this 
view cannot be held. It is rather an expression of the great 
delay in the process of fusion of the gametes, for which the alga 
is remarkable. 
Fig. 2, A, also drawn from a permanently mounted specimen, 
shows the commencement of fusion. The walls of the protuber¬ 
ance (c) of the conjugating cells have become much swollen and 
mucilaginous, and are seen to have been torn apart in the 
mounting. The septum (b), which cut of the gametangium in the 
upper cell, is retained by the cell-wall of the latter, its attachment 
to which is clearly shown. The upper gamete has been torn from 
its outer investment, but is surrounded by its inner wall (a), while 
the specimen shows that the latter is an independent structure 
The lower gametangium (in the figure) is intact and its wall 
obviously double. 
The earliest indication of the commencement of fusion of the 
gametes is quite characteristic, the appearance being that shown 
in Pig. 1, D, a. The outer wall of each gametangium (i.e., the 
walls of the original protuberances) is seen to have become much 
swollen and mucilaginous, the line of separation between the two 
gametangia being lost. One of the gametes (the lower one in the 
figure) now puts out a conical process towards the other gamete, 
hut the latter, instead of putting out a corresponding process, 
exhibits a flattening or slight concavity on its surface where the 
process impinges on it. This concavity is shown in the upper 
