Reproduction of Cystopus Candidas, Ldv. 321 
Formation of the Oosphere and Fertilizing Tube. 
In the denser and more granular protoplasm on the side 
of the oogonium nearest to the antheridium, already noticed, 
a hyaline space appears, from which a papilla with a deeply 
stained apical spot projects towards the antheridium, tending 
to bore its way through the wall of the oogonium and causing 
the wall to become somewhat thinner at this place. The 
protoplasmic contents of the antheridium appear to be con- 
tracted at first in front of this projection and a slight 
depression is produced (Fig. 6) ; but soon a dense granular 
mass appears in the antheridium, on the side nearest this 
projection, and a fertilizing tube is put out which penetrates 
the oogonium at this spot (Fig 10 ). This however does not 
take place until the formation of the oosphere has com- 
menced. The receptive papilla, as we may call it, is very 
clearly located in the oogonium by the contraction of the 
protoplasm from all parts of the wall except at this point, 
where it appears to be securely attached, and remains so 
during the whole of the time required for the development 
of the fertilizing tube. While these changes are taking place 
the nuclei, both of the oogonium and antheridium, increase 
considerably in size. The network becomes more distinct 
and stains more deeply, so that its granular nature can be 
easily made out. 
The differentiation of the oosphere now begins. The 
protoplasm contracts towards the centre into a roundish 
mass, connected to the wall of the oogonium by thick pro- 
toplasmic strands (Fig. 8). This central mass contains all 
the nuclei ; none are to be found in the thick peripheral 
strands of protoplasm. It gradually becomes further differ- 
entiated into a central vacuolate and reticulate mass which 
stains with a reddish tinge, and an exterior peripheral layer 
of very dense non-vacuolate protoplasm, the periplasm, which 
stains with a bluish-red tinge. The whole of the protoplasmic 
contents of the oogonium outside the oosphere become finally 
condensed into this periplasm, with the exception of a few 
