350 Bower,- — On antithetic as distinct from 
the progress of the sporophyte from small beginnings in 
the lower Bryophytes to large size and great complexity 
of form and structure in the Vascular Cryptogams and Gym- 
nosperms ; its advance is accompanied by a corresponding 
reduction of the oophyte, and the whole is to be correlated 
with a progression from the aquatic or semi-aquatic habit 
of the lower forms, to the very distinctly sub-aerial habit 
of the higher. Taking all these points into our general 
view, it may be concluded that the alternation which is so 
prominent in the main archegoniate series is the result of 
adaptation of originally aquatic organisms to sub-aerial con- 
ditions of life : it may, in fact, be distinguished physiologically 
as an amphibious alternation , which finds its morphological 
expression in the difference of external form and internal 
structure between the more ancient gametophyte and the 
more recent sporophyte. 
Regarding the archegoniate series from the point of view 
of descent, it is seen that the alternation must have been 
the result of interpolation of a new development between 
successive gametophytes, an intercalation of a new stage 
more especially adapted to life in air rather than in water 
— that intercalated stage being what we recognise as the 
sporophyte : this being so it is no matter for surprise that 
it should usually differ from the gametophyte in external 
form, though it may at times simulate it to a greater or 
less degree. Accordingly this alternation in the archegoniate 
series may from the phylogenetic point of view be styled an 
alternation by interpolation of a new sub-aerial phase between 
the pre-existent semi-aquatic ones : or, if the introduction of 
new terms be thought undesirable, this alternation may be 
called after Celakovsky 1 an antithetic alternation. 
It is a direct outcome of this view of the origin of the 
sporophyte by interpolation of a new phase, which edged its 
way in, so to speak, between successive gametophytes, that 
it cannot itself be a gametophyte which has undergone a 
Sitz. d. Ges. d. Wiss. in Prag, 1874, p. 30. 
