592 
Notes . 
be unwise to leave the consideration of these phenomena altogether 
on one side. Not only can no sharp line be drawn between variations 
(the use of which in evolutionary questions none will deny) and mon- 
strosities, but, apart from the particular organic forms which result, 
we appear to be dealing with a capability of many — perhaps all — 
Fern-prothalli to assume characters of the sporophyte; a general 
property of the gametophyte of this kind cannot be disregarded 
A fuller knowledge than we possess of the causes of apogamy is, 
however, necessary before the bearing of the phenomena on the 
nature of alternation can be properly estimated ; such knowledge may 
lead to an explanation more in accordance with the antithetic theory 
than any which has yet been given. 
Whether the homologous or the antithetic theory is to be con- 
sidered the more probable has an obvious bearing on morphology. 
But there is a wide difference between considering the two generations 
homologous with one another in the sense that the spore-bearing 
generation is ultimately to be traced back to modification of the sexual, 
and the view that any special structure of the sporophyte is strictly 
homologous by descent with any structure in the gametophyte. 
Special evidence would be necessary before such a conclusion could 
be drawn, and, so far as I am aware, no such case has been shown 
to exist. Not only, then, does the question of the nature of alter- 
nation of generations in the Archegoniates appear to be an open one, 
but there seems no reason to apprehend confusion in comparative 
morphology, whichever of the two theories be adopted as a working 
hypothesis. 
In concluding this account of some of the main factors in the 
problem which is the subject of this discussion, three subsidiary 
questions may be suggested — the probable line of descent in arche- 
goniate plants, the bearing of the cytological facts on the question, 
and the significance to be attached to apospory and apogamy. None 
of these questions, any more than the general one of the nature of 
alternation, may admit of a decided answer. It can, however, hardly 
fail to be productive of good if this discussion enables us to see our 
way more clearly to the directions in which the answers to these 
problems must be sought. 
W. H. LANG. 
Queen Margaret College, Glasgow. 
