Igor | GAMETOGENESIS AND FERTILIZATION IN ALBUGO 167 
nucleus of an individual gamete. The fact that Phycomycetes, 
in conidia and oospores, sometimes lose the ability to individ- 
ualize their units has an important bearing on the problem. 
It is well known that the contents of conidia and oospores 
ordinarily separate into as many regions as there are nuclei, 
and that these develop into zoospores, each unquestionably an 
individual. However, if these spores, by a change of external 
conditions, are induced to germinate by means of a tube, the 
zoospores do not emerge as individuals. Not merely is there 
a failure to resolve the protoplasm into individuals, but there is 
an actual surrender of individuality after it has been attained. 
Not only does this occur in ontogeny, but it is a very generally 
accepted belief that it likewise occurred in the phylogeny of 
this group. In the more primitive forms which germinate by 
zoospores individualization is not abandoned but is merely 
delayed, since in germination each fusion nucleus or each of its 
immediate descendants develops its own plasmoderma and begins 
independent life. In such form the phenomenon is comparable 
to delayed wall formation in endosperm, with the remarkable 
exception that in Albugo fertilization occurs during the period 
of delay. 
Pyronema (Harper 1900) may be regarded as an excellent 
illustration of a condition .in which the individuality of the 
sexual nuclei habitually finds expression only through their 
behavior in the act of fertilization. The manner in which the 
fusion nuclei wander away immediately after fertilization, and 
the absence of units in the cytoplasm, are strikingly similar to 
Albugo, as are also the mitoses of the nuclei during oogenesis, 
the marshaling of the nuclei into a hollow sphere, the participa- 
tion of the oogonium in the dissolution of the wall adjacent to 
the antheridium; even the trichogyne resembles in many respects 
the receptive papilla of Albugo. 
While certain Ascomycetes resemble the Florideae more 
than they do the Phycomycetes, the points of similarity men- 
tioned above between the Phycomycetes, Albugo, and Pyronema, 
are sufficient to justify careful scrutiny of all features before 
