. 
1904] DAVIS—OOGENESIS IN VAUCHERIA 89 
in Vaucheria offers further difficulties for such a theory. RUHLAND 
(703) is also unwilling to follow ROsENBERG in his theory of reduction. 
For these reasons the writer believes that the mitoses in the oogonia 
and antheridia of the Phycomycetes have no special significance, or 
are merely the remains of nuclear divisions that were formerly char- 
acteristic of simpler types of gametangia or perhaps the primitive 
sporangia that preceded these. 
The simple precesses of oogonesis in Vaucheria seem to prove 
conclusively that all of the nuclei in the oogonium are homologous 
and potentially gamete nuclei, and this supports HARTOG’s suggestion 
for Saprolegnia of many years ago. The author believes this to be 
equally true of the nuclei in the gametangia of the Saprolegniales 
and the Peronosporales. The mitoses in the last two groups have 
complicated the problem, but there seems now to be no special sig- 
nificance in these divisions, since they are not only variable in num- 
ber, but may be entirely absent. Thus there are two mitoses in 
Albugo and Plasmopara, but only one in Saprolegnia, certain species 
of Peronospora, and Pythium, and they are entirely absent in the 
species of Vaucheria just described. 
There are then excellent reasons for considering all of the potential 
and functional gamete nuclei in Vaucheria, Saprolegnia, and the 
Peronosporales as homologous, and there seems to be little doubt 
but that the oogonia of all these forms are related at least as game- 
tangia through remote ancestors, if not as fully differentiated oogonia. 
The problems then concern the exact relationships between the 
eggs of Vaucheria, Saprolegnia, and forms of the Peronosporales. 
Are these female gametes strictly speaking homologous, or have they 
been developed along somewhat different paths? An old view, and 
that probably held by most botanists, is one of strict homology, 
implying an intimate relationship between these fungi and Vaucheria. 
It is a problem of fundamental importance in all discussions of 
phylogeny in this region of the plant kingdom, and of special con- 
cern to those who make Vaucheria the starting point of a series of 
fungi beginning with the Peronosporales or the Saprolegniales and 
ending in the Mucorales. 
From all points of view oogenesis in Vaucheria is simpler than in 
the Saprolegniales or Peronosporales. It conforms perfectly to well- 
