04 . BOTANICAL GAZETTE [avcusr 
coenogamete would be larger and well supplied with food material, 
and might finally develop one or more eggs and thus become an 
oogonium; the male coenogamete in contrast would remain small or | 
perhaps become further reduced and would be called an antheridium 
when it bore a sexual relation to an oogonium. Thus conditions 
like these of the Saprolegniales and Peronosporales might arise from 
coenogametes resembling those of the molds, and a condition of 
heterogamy result, which would closely resemble that of Vaucheria 
and yet have no genetic relation to the latter condition. The eggs 
of the Saprolegniales and Peronosporales in such an event would 
have an origin entirely independent of any other line of sexual evolu- 
tion, and with the conspicuous peculiarity of coenocentra marking 
the position of dynamic centers during the process of oogenesis. 
A question sure to be raised in this connection is the possibility es, 
of undifferentiated coenogametes of the mold type arising through 
the simplification or degeneration of organs like the antheridia and 
oogonia of the Saprolegniales and Peronosporales. Such a line of 
evolution would demand the suppression of some very highly differ- 
entiated cell processes, such as the extensive nuclear degeneration, ie 
the formation of coenocentra, and the differentiation of periplasm. = 
_ There is no evidence of such tendencies among the forms in question, ns 
but, on the contrary, excellent reasons for believing that the direction — 
of sexual evolution is toward greater and more precise protoplasmic 
complexity rather than simplification. The point is especially weE 
illustrated in the series of species in the genus Albugo, where the limes 
is clearly from the multinucleate egg and small coenocentrum of A. 
Biliti to the uninucleate egg and extraordinary large coenocentra of es 
A. candida and A. Lepigoni. The author can see at present a 
probability of a line of sexual degeneration or simplification ah = 
higher forms toward the molds. a 
For these reasons we are driven to consider the possibility ofa es 
origin of the coenogametes of molds from gametangia that have - 7 
passed the stage of isogamy. I have previously (DAVIS ‘00 Ps 777 
and ’o3, p. 335) advanced the hypothesis that such coenog®” 
may have arisen from gametangia somewhat like those DOW" 
among the lower Siphonales and in Cladophora. These es genes : 
are generally terminal structures that discharge motile gamet i 
