io8 Discussion on “ Alternation of Generations 
resembling in form find organisation the sexual one, but with diploid 
cells and reproducing by spores formed after a reduction division. 
Such cases as Dictyota and Polysiphonia are the new wine that 
threatens to hurst both the antithetic and homologous wine-skins 
as originally sewn up by Celakovsky and Pringsheim. 
I do not venture to anticipate what may be an ultimate complete 
explanation of alternation of generations. Nor do I wish to put out 
of account the possibility of the different states of the specific cell 
being shown to have some causal influence on the differences of the 
resulting individuals in archegoniate plants. In stating this 
ontogenetic hypothesis before you, I am not concerned altogether 
with its truth. It is an attempt to look at the question in the light 
of the new, if imperfect, facts before us. The value of such an 
hypothesis lies in its use as a working tool, more than in its truth. 
I am in the position of a surgeon exhibiting a new instrument, with 
which he has never performed a major operation, but which he 
hopes may prove of use in his own hands or in those of more skilful 
colleagues. This working hypothesis may be of use in directing to 
new lines of enquiry and experiment, some of which may test the 
hypothesis and support or disprove it. The critical experiment 
would he to get, e.g., the fertilised egg of a fern to develop free, 
under the conditions that usually act on the spore. On my view it 
should give rise to an individual with the form and organisation of 
the prothallus. The converse experiment, of placing the spore 
under the conditions of the zygote, is less practicable. Such 
experiments are wanting, but some of the facts ascertained regarding 
induced apogamy and apospory appear to approximate to these 
results. 
Professor Bower, who opened the discussion, said that it might 
have been reasonably expected that after so important a commu¬ 
nication as that by Dr. Lang, the President should speak first; 
but he thanked the President for permitting him to follow Dr. 
Lang, so that he might give some explanation of the bearing of the 
views now submitted upon the position of those who had upheld 
the antithetic theory in its old form : this would clear the ground, 
and make plainer the issues as they would now stand. He hastened 
at once to admit the cogency of the ontogenetic view now pro¬ 
pounded ; but the position of Dr. Lang appeared to him to be that 
of presenting a new aspect of certain most important facts relating 
to alternation, rather than in itself a new theory. Dr. Lang did 
not probe into the ultimate origin of the two phases of the life- 
cycle, _but dealt with them as already established, leaving the 
question of the ultimate origin of the generations very much where 
it was. What the new ontogenetic view did do was to modify very 
profoundly the aspect of the sporophyte in the two series of the 
Archegoniatae: under the old antithetic theory the sporophyte 
was assumed to have been dependent ab initio ; its dependence 
would not now be held to be primary, but secondary, and we should 
contemplate the encapsulation of a generation originally free. If 
this were accepted, then the great bugbear of those who held by 
homologous alternation in the past, (viz. the origin of the whole 
archegoniate sporophyte from a body primitively fertile throughout, 
by a process of sterilisation) would fall away, for the subsumed 
generation might have been already provided with both sterile and 
