LICHENS AND RECENT CONCEPTIONS OF SPECIES. 
BY BRUCE FINK. 
The biological atmosphere is pregnant with ideas regarding species 
and their evolution. We are brought face to face with the “fluctua- 
tion” view of Darwin and the more recent one of “discontinuous varia- 
tion” of Bateson, later called “fluctuation” by de Vries. Pangenesis has 
received prominent attention in the discussions regarding evolution; and 
Weismann formerly thought that germinal selection accounted for all 
evolution though, in his recent work in two volumes, he admits that 
conditions of environment may affect the soma when acting continu- 
ously through many generations. Another extreme view is that 
expressed by Jordan in a recent number of “Science”, to the effect 
that isolation plays a part in the evolution of every species. De Vries 
has not told us that his “mutation theory” accounts for all evolutioa 
of species, but he says, — “systemic and physiological facts seem to indi- 
cate the existence of universal laws, and it is not probable that the 
process of production of new species would be different in the various- 
parts of the animal and vegetable kingdoms.” 
The view expressed by de Vries in the above quotation, as well as 
the attempt formerly made by Weismann, to account for all evolution 
through germinal selection, is in accord with the philosophical views 
of the monist and the pantheist, and since the latter author has now 
admitted the possibility of environment being a factor in evolution and: 
the former never denied this, both views of evolution seem reasonable 
enough. 
However, when we consider the limited time spent in the observa- 
tions of de Vries, we may still question whether he has really dis- 
covered “elementary species” or merely sports. And furthermore, admit- 
ting the validity of his ‘elementary” species, we may doubt whether 
large numbers of “elementary species” will ever be well known and 
kept in mind long enough for any other use than that of determining 
the role of mutation in the evolution of species. L. H. Bailey bewails 
the fact that “we study plastic material; at the same time that we are 
making a desperate effort =5- * * toward rigidity of noniencdature”. 
He also tells us that systematists do not distinguish, in describing spe- 
cies, between characters of great and those of small or no physiological 
value. Apropos of this idea comes the parallelistic view that there caa 
be no morphological evolution of characters without a correlated func- 
tional or physiological advance, and the parallelistic viev/ aside, it is 
generally conceded that, though a structure may begin to appear through 
hyper-nutrition, it usually soon takes on some function or the hyper- 
trophy simply produces a morphological monstrosity, which soon disap- 
pears in phyletic evolution, through atrophy. There seem to be a few 
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