i i 2 Discussion on “ Alternation of Generations .” 
present position of the question as it affected the higher plants, in 
which his chief interest lay. 
Professor Farmer remarked that in spite of what had been put 
forward, he still appeared as an entirely unrepentant and unre¬ 
generate sinner so far as his attitude towards the alternation of 
generations was concerned. He desired to pay a tribute of 
admiration to the work of Lang and of Schenck, as having served 
to concentrate attention on new and suggestive points of view. 
But he did not believe that any insight was afforded thereby into 
the causes which in the first instance were responsible for the 
cyclical alternation, nor did he think that the rival claims of the 
homologous and antithetic theories were capable of being decided 
on such lines. The matter was one of actual history, but the 
difficulty was that we could neither ascertain directly how the real 
course of events proceeded, nor could we, in attempting to recon¬ 
struct them, agree as to the criteria which might be decisive. 
Much had been made of cytological criteria. The common 
association of the haploid condition with the gametophyte, and of 
the diploid with the sporophyte had appealed to many as indicating 
a causal nexus, and so long as the coincidence was without exception 
those who urged post hoc ergo propter hoc, occupied a strong position. 
But it was evident that this reliance upon a supposed physiological 
cause was bound at once to prove illusory, on the discovery of the 
first well-founded exception. The facts of apospory and apogamy, 
as soon as their cytological features were cleared up, shewed that, 
regarded as a cause, neither of the cyclical nuclear changes involved 
in fertilisation and in meiosis respectively, could any longer be 
regarded as necessarily, or causally, related to those other cyclically 
occurring morphological changes in plants which exhibit alternation 
of generations. The two events were cyclical, and they might be 
coincident, but more than this could hardly be seriously urged, 
especially when the fact was remembered that the nuclear processes 
in question were not only of general occurrence in the higher 
animals and plants and the processes by which they were respectively 
brought about were similar in these widely diverse organisms, but 
that they occurred just the same, even when alternation of 
generations was either lacking altogether or was associated with 
other points in the life-history. 
It seemed quite probable that alternation might differ in 
character in different phyla, whether it was homologous or antithetic. 
That it was intercalated was a question that must be decided on 
grounds other than cytological. 
The case of Dictyota had already been mentioned by others, 
but it seemed to gather in interest if taken together with Fucus — 
always a puzzle to the alternationists. The speaker would be quite 
prepared to admit the probability of homologous alternation in 
Dictyota (although not perhaps for the same reasons that had been 
urged by others), and especially when it was regarded in connection 
with Fucus. In the latter plant, the so-called oogonium first existed 
as a diploid cell. The oogonial nucleus then passed through 
meiosis, and the four resulting nuclei lying free in the protoplasm, 
waited for some time before undergoing the final division whereby 
the eggs were produced. The oogonium was thus a “ tetra- 
sporangium ” first, owing to the onset of meiosis in the sexual cycle 
at this particular stage. In Dictyota we had the escape of the 
