230 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
phylogenetic reminiscence, it is the active agent in bringing about 
fertilization. Even in this divergence from other forms studied, a 
careful review of the facts observed, particularly by Wager, Trow, 
and Miyake, shows that there is considerable variation in the degree 
of development of the antheridial tube in different species. For 
example in figures 4 and 5 of Wager’s (:00) paper there are no 
indications of the walls of the antheridial tube and even in figure 7 
it has a well developed structure little farther than the periplasm; 
moreover, both Trow and Miyake, as previously mentioned, 
expressly state that they cannot trace the tube beyond the peri¬ 
plasm. Viewed from this standpoint, these forms with their poorly 
developed and evanescent tubes, evidently stand between Araiospora 
on the one hand and such forms as Albugo with its highly special¬ 
ized tube on the other and tend in a measure to bridge over the 
wide gap between them. One would naturally expect that the 
Pythium would also show little or no evidence of an antheridial 
tube — a supposition that seems to be borne out by the facts. 
The antheridium .— There is little of special interest in the devel¬ 
opment of the antheridium. Early in its history it bends down and 
applies itself closely to a small portion of the oogonial surface near 
the base of the oogonium. At this time it usually contains from 
five to seven nuclei. No nuclear divisions were observed here 
but it is quite probable that a general mitosis occurs, since old 
antheridia are found that contain about double this number. Previ¬ 
ous to this nuclear division the cytoplasm consists of a uniform 
alveolar meshwork (pi. 13, fig. 17). This particular antheridium 
contains five nuclei, two appearing in a succeeding section. These 
nuclei take the stain similarly to those of the oogonium which they 
otherwise resemble. Just before fertilization,’ the cytoplasm 
becomes more dense and stains more deeply (pi. 12, fig. 16; pi. 15, 
fig. 32). After fertilization the remaining cytoplasm and nuclei may 
persist for some time or both may contract into a small mass and 
degenerate. 
Fertilization. 
In following the development of the fine meshed ooplasm, the 
egg itself has been described. It consists, when ripe, of a differen¬ 
tiated central region, which at this time contains a nucleus and 
