364 Bower . — On antithetic as distinct from 
ascendency. When, as in the preceding sketch, we consider 
what the results of the migration from water to land must 
have been, the permanence and constancy of the antithetic 
alternation explains itself. The permanence or morphological 
fixity of a phenomenon in any phylum is in a sense propor- 
tional to its importance in the well-being of the organisms : given 
a conservatism in the mode of fertilization (which I confess is 
difficult to explain), the rise and progress of the sporophyte in 
the archegoniate series, and the constant recurrence of the 
antithetic alternation, appear to me to be a natural outcome of 
the migration from water to land 1 . 
It is much more difficult in the Florideae and Ascomycetous 
Fungi to recognise or suggest what circumstances may have 
led to the interpolation of the neutral phase in their life-cycle : 
it is out of the question that the conditions have been the 
same as those which, according to the above view, conduced 
to the antithetic alternation in the Archegoniatae : while we 
recognise the chief determining conditions for these, the 
absence of such in the case of the Florideae and Fungi would 
be an additional reason for not considering the interpolated 
phase in them as strictly comparable to that in the Arche- 
1 Professor Geddes, in his recent work on the ‘ Evolution of Sex/ writes concern- 
ing the rationale of alternation as follows (p. 214) : — 
‘ A survey, in fact, of the conditions and characteristics of the two sets of forms, 
inevitably leads us to regard the asexual generation as the expression of predomin- 
ant anabolism, and the sexual is equally emphatically katabolic. Alternation of 
generations is, in fine, a rhythm between a relatively anabolic and katabolic pre- 
ponderance.’ 
I leave zoologists to deal with this generalisation from the zoological point of 
view ; as applied to plants I dissent from it entirely. If we regard only the Fern, 
I will admit that the prothallus is smaller than the Fern-plant, and that the two 
follow one another in alternate succession ; if this be all that is meant by the 
turgid phrase ‘a rhythm between a relatively anabolic and katabolic prepond- 
erance/ the above quotation may in a sense be accepted as applicable to Ferns. 
But how is the above statement to be applied in the case of the Moss or Liver- 
wort ? It is obviously absurd to say that the large green assimilating gametophyte 
of Marchantia shows ‘relatively katabolic preponderance/ while the minute 
parasitic sporophyte is the expression of ‘ relatively anabolic preponderance.’ 
Professor Geddes appears to me to have made his generalisation while he had only 
the Fern in view, and his conclusion is entirely inapplicable to alternation in plants 
at large. 
