AFFINITIES AND CLASSIFICATION OF ALG, 51 
that, although the system of classification of Thallophytes above 
alluded to has been adopted by a few authorities in this country 
and on the Continent, it has not met with general acceptance, 
The adoption of its leading principle, that “in each class Fungi 
have diverged as ramifications from various types of Algæ,” * is 
seen to lead to such startling results as the collocation in the 
same class of Spirogyra and Mucor, of Volvox and Peronospora, 
of Callithamnion and Agaricus. It may, on the contrary, be 
safely asserted that several of the most important groups among 
Fungi (take, for example, the Mucorini, the Uredinew, and the 
Basidiomycetes) display no traces of genetic affinity with any 
known class of Algæ ; and if, on the other hand, we have forms 
like Saprolegnia and Chytridium, or Leptothrix and Beggiatoa 
. among Protophyta, which betray strong indications of a degraded 
affinity with groups of Algæ, this by no means contradicts the 
general law that Fungi as a class form an altogether independent 
series, 
Retrogression may take the form of the suppression of either 
the vegetative or the reproductive organs; and wherever you 
have one of these sets of organs displaying strong development, 
while the other set of organs is very feeble or altogether wanting, 
you have prima facie evidence of retrogression. To take examples 
from the class of Fungi. It seems highly probable that the 
Myxomycetes, in which the whole vegetative structure is sub. 
ordinated to the mode of reproduction, are derived from some 
higher class of Fungi by retrogressive metamorphosis ; while, on 
the other hand, in many families of the Ascomycetes the sexual 
organs have partially or entirely aborted ; and it is possible that 
the Basidiomycetes are a class in which this suppression has pu^ 
Still more completely carried out. Examples from Alge wi 
o i sequel. . 
“Te is somewhat singular that, if the principle which I have beon 
advocating is sound, it brings us back a long way towards the 
time-honoured classification, but of late years almost abandoned, 
of the Algæ into Chlorospore®, Rhodospores, and Pheosporex— 
and the brown. ; 
the keener = na if, at a very early ‚period in the develop- 
: f vegetable life, three distinct kinds 
ment of the simplest forms o eg r a 
i re 
of cell-contents were differentiated, 1 presenting three distinct 
modes of life, and possibly three distinct lines of descent from 
* Op. cit. p. 244, footnote. 
MISSO! 
Bryr A KY f 
