Notes. 
586 
our view to archegoniate plants, the essential distinction of the 
antithetic and homologous theories will become plain. Further, 
we shall here be dealing with a problem with regard to which the 
work of Professor Klebs justifies the anticipation that direct evidence 
will sooner or later be obtained. The main question at issue is, 
In what relation does the group of spores in Oedogonium , or the 
small mass of tissue resulting from the division of the fertilized 
ovum in Coleochaete , stand to the asexual individuals of the same 
species? There is some evidence that in this stage we see the 
representative of an asexual individual, the vegetative body of which 
has become more or less completely reduced. Thus occasionally 
in Oedogonium a vegetative individual develops from the zygote; 
in Uothrix the zygospore develops a rhizoid, but the contents of 
what appears to be a rudimentary plant are wholly devoted to the 
formation of motile spores. On this view the cell-mass in Coleochaete 
would be regarded as a reduced thallus, all the cells of which form 
spores asexually. The reduced generation which proceeds from the 
zygote would genealogically correspond to an independent asexual 
individual, and just as the latter is homologous with a sexual individual, 
so would the four spores in Oedogonium or the cell-mass in Coleochaete 
be. This would be homologous alternation of generations. 
But the same facts can be viewed in another light. In all these 
cases the advantage to the plant in producing almost at once 
a number of individuals instead of one as the result of the sexual 
act is obvious. The division of the ovum may have originated as 
a special adaptation to this end, and not represent a reduced first 
neutral generation at all. Jn the life-history of these plants there 
would then be a stage not represented in the majority of the Thallo- 
phytes, which may in this sense be spoken of as interpolated. The 
cell-mass of Coleochaete upon this view' would not represent a less 
reduced neutral generation, but a more complicated development 
of the interpolated stage, which is seen in its simplest form in 
Oedogonium. This stage would not correspond to, or be homologous 
with, the independent asexual individuals, and leaving these out of 
account, only one individual, and the result of elaboration of its 
zygote would be represented in the life-history. The alternation 
would not be homologous but antithetic. 
If we now proceed to apply these two points of view to the facts 
of alternation in the Archegoniatae, the problem in its most general 
