The British Freshwater Algce. 141 
of the consideration of the reproductive processes of Algae. The 
treatment of gamogenesis and sex is not unexceptionable. On p. 15 
it is clearly implied that all gamogenesis among Algae is sexual 
i.e. depends on the union of a male and female cell. Surely this 
is most misleading to the student. In the most primitive types 
“ sexual differences ” cannot be truly said to be “ scarcely 
appreciable ”; they simply do not exist, and on this fact depends 
the whole modern theory of the evolution of gamogenesis. The 
word *• sexual ” is much better confined to types where there is a 
clear binary differentiation between the gametes, though unfortu¬ 
nately the term is constantly used as a synonym for “ gamogenetic.” 
But in this latter sense the phrase “ sexual differences ” has 
no meaning. We cannot see the advantage of describing 
the fertilization-process of Rhodophyceae as “ carpogamous 
heterogamy,” with “ no specially differentiated female cell.” The 
fact that the carpogonial cell may be externally similar to the other 
cells of the carpogonial branch does not seem to warrant the 
implication that the process of fertilization differs in any essential 
respect from that obtaining in other algae ; nor does the 
“ carpogamy ” properly qualify the “ heterogamy.” 
The treatment of alternation of generations is also, we think, 
too formal, and suffers from the absence of the evolutionary point 
of view. We may fairly say that no one would have spoken of 
an alternation of generations among the Algae if it had not been for 
the phenomena of alternation seen in the Archegoniatae. The 
phenomenon of the division of the zygote into a number of cells, each 
of which gives rise to a new plant, is not, in origin, an alternation of 
generations at all, but merely a phenomenon of polyembryony. 
The most that can fairly be said is that it foreshadows the 
development of a complex and semi-independent fruit-body such as 
we see in the higher Bryophytes, and, on the “ antithetic ” theory 
of Celakovsky and Bower, the true alternation of distinct individuals 
seen in the Pteridophytes. On the “ homologous ” theory the 
Algae may foreshadow the Pteridophytic alternation in another way ; 
for we may conceive that an Alga reproducing itself both by 
gametes and by zoospores might acquire a rhythm or periodicity of 
such a nature that each mode of reproduction became restricted to 
alternate generations, and thus gave rise to the state of things that 
we have in Dictyota. So long as we remain in ignorance of the 
nuclear reduction-phenomena in the green Algae, all this must of 
course be purely speculative, and Mr. West may perhaps be of 
opinion that a discussion of such topics is out of place in the 
