of Pilularia globulifera , L . 249 
broader and shorter, indicating a separation of the chromatin- 
masses of which the body is composed. In all the later stages 
(PI. XIII, Figs. 38-39) the spermatozoid, sp ., had assumed 
much the appearance of an ordinary nucleus, nearly round in 
shape, and in close contact with the nucleus of the oosphere. 
The actual fusion of the two nuclei was not observed, but 
there is no reason to doubt that, as in other cases 1 observed, 
the cavities of the two nuclei are thrown into direct com- 
munication, and that the contents of the male nucleus flow 
into the cavity of the female nucleus, thus completing the act 
of fecundation. 
The nucleus of the oosphere (PI. XIII, Figs. 38-39) is large 
and has a well-marked membrane, but although a membrane 
may be present in the male nucleus, it is certainly much less 
evident, and it is by no means improbable, that a definite 
membrane is not developed. 
The upper part of the oosphere, about one-third (PL XIII, 
Fig. 38), is nearly transparent, and constitutes the so-called 
receptive spot. This is traversed by what look like con- 
tinuations of the granular protoplasm of the lower part of the 
oosphere. The nucleus at this stage presents the appearance 
of a transparent vesicle, containing a faintly-marked net-work 
of fine filaments which do not stain readily, and a small 
amount of chromatin. 
How long after the union of the two nuclei the first 
division in the fertilized germ-cell takes place could not be 
exactly determined, but it is probably within two or three 
hours, and possibly even sooner. In one case the germ- 
cell was observed undergoing division. In this instance 
(PI. XIV, Fig. 1) the daughter-nuclei were already complete, 
but the cell-wall was not yet complete. The nuclear spindle 
was still very evident, and in the middle lay the cell-plate, 
showing plainly the separate elements of which it was com- 
posed. 
If for any reason the germ-cell fails to become fecundated 
the prothallium may continue to grow for some time, but this 
1 Strasburger, Ueber Kern und Zelltheilung im Pflanzenreiche, 1888, pp. 225-449. 
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