1904] DAVIS—OOGEN ESIS IN VAUCHERIA 95 
But should organisms of this type (whether algae or fungi) be placed 
under conditions unfavorable for the formation of motile gametes, 
the gametangia themselves might be expected to act as coenocytic 
units, and obeying the chemotactic influences of sexual cells fuse 
with one another as coenogametes. 
So the problems of phylogeny in this higher region of the Phy- 
comycetes become greatly complicated through factors that concern 
the environment and life-habits of the forms in question. The 
absence of pores in structures that at one time evidently formed 
motile gametes presents great difficulties: to the establishment of 
relationships between the Mucorales, Saprolegniales, Peronosporales, 
and Vaucheria. Yet, it may be that the suppression of this structure 
indicates little more than a change in life-habit from an aquatic, to 
an aerial existience (Mucorales) or to a parasitic life (Peronosporales), 
with the apogamous Saprolegniales presenting conditions peculiar to 
themselves. But until we know more about these life-habits and 
the possibility of an organism passing from one condition into another, 
it is pure speculation to lay out lines of relationship. And again, we 
lack knowledge of the processes of oogenesis in a number of forms 
which may have important bearings on these problems of phylogeny 
(especially for Monoblepharis and Sphaeroplea). 
In spite of the complications of the problems of phylogeny in the 
Phycomycetes, certain features stand out clearly which may be 
briefly summarized. The multinucleate character of the sexual 
organs in types of the Mucorales, Saprolegniales, and Peronosporales 
thus far studied, and perhaps some other forms as well (Monoble- 
pharis) is likely to prove universal in these groups. Numerical 
reduction of potential gamete nuclei takes place through degenera- 
tion, a process of great physiological interest which deserves careful 
study. The suppression of the pore-forming activity gives the closed 
oogonium and antheridium peculiar to the fungal groups. The 
coenogametes characteristic of the Mucorales and also illustrated by 
certain of the Peronosporales (Albugo Bliti, A. Portulacae) are 
morphologically gametangia and probably have had their origin by 
the suppression of the processes of cleavage to form many gametes 
and their assumption as coenocytic units of sexual attributes. The 
Saprolegniales and Peronosporales exhibit the further peculiarity of 
