150 BOTANICAL GAZETTE [FEBRUARY 
the enormous size of 50-60 (figs. 15, 45). This size, however, is 
attained only in the largest zoosporangia. The nuclei of the 
resting spoftes are never so large as those of the zoosporangia, 
which themselves vary greatly, being roughly proportional to the 
cysts in which they occur. In extremely small cysts the nucleus 
may never exceed 15 #, though few are smaller than 20 at maturity. 
In the largest nuclei the increase in volume during growth is almost 
10,000 fold. There are but few organisms in which any single 
nucleus grows to such an extent without division, but Rhodochy- 
trium is by no means unique in this respect. In Synchytrium, by 
reason of the minuteness of the zoospores, the increase is very much 
greater, amounting sometimes to 50,000 fold. In some of the 
cycads, especially Dioon (CHAMBERLAIN 5), the increase in volume 
must be nearly as great, since the mature nuclei reach 500-600 # 
in diameter. The nuclei of some animal eggs, for example Dytiscus 
(DEBAISIEUX 7), also show great increase in volume, but not so 
much as in the plants just cited. 
For the study of the vacuolation of the nucleolus, Rhodochytrium 
and Synchyirium probably afford better opportunities than any 
other organisms, although an analogous process occurs in many 
plants. Occasionally in Rhodochyirium a single central vacuole 
appears to increase in size until only a thin rind of stainable sub- 
stance remains. In. other cases the whole nucleolus becomes 
honeycombed with numerous small vacuoles (fig. 46), which later 
coalesce (fig. 47) into a large central cavity (fig. 44), which con- 
tinues to increase in size until finally the old nucleolus, originally 
a karyosome, becomes a plasmosome, collapses (fig. 45), dis- 
integrates, and finally disperses in the cytoplasm during mitosis. 
Intimately connected with the history of the nucleolus, and in 
many ways perhaps even more interesting, is the behavior of the 
chromatin. As may be seen from figs. 2, 12, 42, the whole of the 
chromatin is at first concentrated in the karyosome, and from it 
all of the chromatin of the primary nucleus is derived. While the 
nucleus is still comparatively small, vacuoles begin to appear in 
the center of the karyosome (figs. 3, 13, 14), and the characteristic 
irregular masses of chromatin begin to fill the nuclear cavity. As 
