22 0 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Development of the Sexual Organs. 
Early development of the oogonium .— Thaxter has described the 
characteristic position of the oogonia. They arise singly or in 
umbels at or near the distal ends of certain segments that in turn 
produce at their upper ends specialized segments upon which the 
antheridia are borne. The zoosporangia, on the contrary, arise 
usually in umbels at the upper end of ordinary segments. In very 
early stages, therefore, there is little danger of confusing young 
oogonia and zoosporangia even in microtome sections. 
As the young oogonium makes its appearance, cytoplasm and 
nuclei flow from the parent liypha into it; and in this process the 
nuclei are frequently elongated. Figure 9 (plate 11) represents a 
section through such an oogonium and its stalk. At this time, the 
nuclei as well as the irregularly coarse and fine meshed, granular cyto¬ 
plasm in the oogonium and the upper end of the parent filament are 
similar. It will also be observed in this figure that the nuclei have 
not at this time taken definite positions in the oogonium but are scat¬ 
tered indiscriminately in the cytoplasm. It may be further seen 
that the nuclei in both structures take the stain so deeply that few 
details of their structure can be made out. Quite frequently even 
the nucleoli of the material fixed in Flemming’s solution were 
masked by the presence of deeply staining materials in the nucleus 
itself; this was particularly true of the nuclei of the sexual organs 
which seemed to take the stain with more intensity than the nuclei 
of the vegetative parts. Figures 9, 10, 11, etc., (plates 11 and 12) 
show nuclei of the young oogonium. 
As nearly as can be determined, this particular oogonium (pi. 11, 
fig. 9) contains nineteen nuclei. Others, however, are on their way 
in (one shown in this section) and there is also an accumulation of 
nuclei in the parent segment near the point where the oogonium 
arises. The wide open stalk, the similar appearance of nuclei and 
cytoplasm in oogonium and parent filament, the small size of the 
oogonium, and the accumulation of nuclei near the base of the stalk 
with some passing in, are evidence that more nuclei will enter the 
oogonium before it is cut off. 
In figure 10 (plate 11) the oogonium has just been delimited. It 
is much larger than the one represented in figure 9 (plate 11) and 
