Discussion on 11 Alternation of Generations .” 109 
fertile tracts. Sterilisation, in any case an important factor, 
would take its place as not necessarily involved in the first steps 
of development of the Archegoniate sporophyte. A consequence 
of this would be to shunt the Bryophytes from their position as a 
key to the origin of the sporophyte : there would not be felt the same 
tendency or perhaps need, as heretofore, to hold them to he 
phyletically isolated. The two great series of the Archegoniatae 
would rather present parallel problems of encapsulation, which 
event might have occurred independently in the two series, and the 
one would not necessarily elucidate the other. Thus Dr. Lang’s 
suggestion would act as harmonising some of the differences which 
existed between the adherents of the two old theories. 
A further effect would he to shift the focus of enquiry from the 
Archegoniatae to the Algae, so far as ultimate origin of alternation 
was concerned. Dr. Lang had remarked that indications were 
wanting among Algae, such as Dictyota, that the sporophyte had 
had any history of gradual interpolation. He (Professor Bower) 
would wish to point out that indications of any other mode in them 
were equally wanting. At the present moment we were in a 
condition of ignorance on that question, which was quite charming. 
One important effect of Dr. Lang’s paper would be to direct 
attention to the study of the Alg£e, and more especially to their cyto- 
logical cycle : this had to he examined in relation to their external 
form. And here it might he remarked that it was unfortunate that 
hitherto attention had been devoted mainly to advanced forms, 
such as Dictyota and Polysiphonia ; it was rather from the com¬ 
parison of simpler forms that evidence as to how the alternating 
generations originated might be anticipated. 
It might be thought from all this that the old antithetic theory 
was gone beyond repair. He did not think that it was. We still had 
each normally completed nuclear cycle presenting two main events—- 
zygote-formation and spore-formation, with the doubling and 
reduction of chromosomes; he was disposed to hold that the 
phases intervening between these two events had been phyletically 
distinct throughout. It might be said that this was not the old 
antithetic theory, and of course it was not, for the whole cytological 
story had been revealed since the discussion of alternations arose ; 
but the two intervening phases corresponded in essentials to the 
phases of the antithetic cycle. A further question which now 
presented itself was this:—if these two phases were phyletically 
distinct throughout their history how far could the parts produced 
upon them respectively he held to be comparable, or be designated 
as “ homologous ” ? Unfortunately the word homologous was used 
with very different significations; there were different degrees of 
homology, the most stringent being that of identical phyletic 
history. It need not be surprising that appendages of the two 
generations should resemble one another, as they did in certain 
cases, being produced from a similar plasmatic basis; but he would 
not regard them as having on that account had the the same 
phyletic history; he would wish to retain the old idea of the his¬ 
torical distinctness of the two alternating phases ; he did not, in 
fact, feel prepared to concede the full morphogenetic unity of the 
spore and the zygote. 
It might be said that such a position was contrary to the 
results of Farmer and Miss Digby, and those of Strasburger, who had 
shown that the chromosome-number did not necessarily determine 
