Discussion on 11 Alternation of Generations.'" 113 
tetraspores, which only after independent life and cell-multiplication 
gave rise to the eggs which in Fucus were produced in the same 
receptacle as the tetraspore. The tetrasporangia might be looked 
upon, in this group, as real homologuesof the oogonia, a comparison 
which was supported by the similarity of the tetraspores to the 
oospheres, which shewed such capacity for parthenogenetic develop¬ 
ment, recalling in this respect what occurred in still less stereotyped 
Phaeophyceae. Although a case for antithetic alternation might 
with consistency be made out, alternation in this group seemed to 
have had a different historical origin, and to have entirely lacked 
features which were present in plants exhibiting what appeared to 
some to be evidence for antithetic alternation. 
In the PolysipJionice there seemed to be other reasons for re¬ 
garding the carposporic organism as representing an intercalated 
(antithetic) phase, and a series shewing increased complexity of 
structure might be readily traced in this phylum from the simpler to 
the more advanced forms. But the confusion introduced by the ille¬ 
gitimate use of meiosis had obscured the meaning of historical 
events, as elucidated by morphological comparison, and led to the 
unwarranted assumption that the tetraspore marked the limit between 
the intercalated new, and the older generation. So far as we had any 
evidence, meiosis itself seemed to have coincided with the formation 
of carpospores in the lower members of the Florideae, and the 
resulting plant propagated itself vegetatively, i.e., within the limits 
of the one generation, by monospores. It seemed not impossible 
that these were the forerunners of tetrasporangia, by the shifting of 
meiosis on to them in the more advanced types. The inter- 
9.45 calated phase, the carposporic plant, might well owe its 
peculiarities of form to its nutritional dependence on the 
parent plant, as Dr. Lang suggested, but this did not touch the con¬ 
ception we might form of it as representing a new, intercalated, 
antithetic, phase in the life-history. 
Again as regarded Coleoclicete ; Allen’s discovery that meiosis 
occurred, not at the formation of zoospores, but at the first 
division of the zygote, seemed to have settled, for some people, the 
intra-oogonial plantlet as representing an example of an homologous 
alternation. General consideration of the relations of meiosis 
indicated that this was a non sequitur. The real point to be decided 
was not the point in the life-history at which reduction occurred, but 
whether the intra-oogonial phase could be regarded as the actual 
descendant of a real Coleochceete plant, modified indeed by its 
retention within the oogonium, but phylogenetically identical with 
the free-living form ; or whether the stages intervening between the 
formation of the zygote and the liberation of the zoospores did not 
represent a new and additional phase intercalated in the life-cycle. 
If this were conceded it would appear to be difficult to escape the 
conclusion that we had in Coleoclicete not only a fine example of 
alternation of generation in the antithetic sense, but also an instance 
of the independence of this condition and that of the meiotic phase. 
The Archegoniatae, again, had to be discussed on their own 
merits. It would seem almost impossible seriously to urge that the 
Bryophytic sporogonium was anything but an intercalated stage in 
the life-history, and that, in the strictest sense of the words, it 
represented an example of antithetic alternation. It would require 
a high flight of imagination to explain how the gametophyte, by any 
conceivable series of modifications actually occurring as historical 
