1895.] Search for the Unknown Factors of Evolution. 419 
important and lasting outcome of this prolonged discussion. 
Weismann is the real initiator of this outcoming movement 
although it has taken a radical direction he neither foresaw 
nor advocated, for his position is eminently conservative. In 
fact his first permanent service to Biology is his demand for 
direct evidence of the Lamarckian principle, which has led to 
the counter-demand for such evidence of his own Selection 
principle, which by his own showing, and still more by his 
own admission in this discussion with Spencer, he is unable to 
meet. His second permanent service, as Professor E. B. Wilson 
reminds the writer, is that he has brought into the foreground 
the relation between the hereditary mechanism and evolution. 
What have we gained in the controversy of the past decade 
unless it is closer thinking and this keener appreciation of the 
necessity for more observation? We carry forth, perhaps, 
some new and useful working hypotheses as to possible modes 
of evolution, and a fuller realization of the immense difficul- 
ties of the heredity problem—but these are only indirect gains. 
It is a direct gain that these negative results have led a minor- 
ity of biologists into a total reaction from speculation and into 
a generally agnostic temper towards modern theories which is 
far more healthy and hopeful than the confident spirit of the 
majority upon either the Neo-Lamarckian or the Neo-Darwin- 
ian side. There is no note of progress in the dogmatic as- 
sertion that the question is established either as Spencer or as 
Weismann would have it, unless this assertion can be backed 
up by proof, and by whom can proof be presented if not by 
these masters of the subject? The conviction we all reach 
when we sift wheat from chaff, and bring together from all 
sources phenomena of different kinds and seek to discern what 
the exact bearings of these phenomena are, is that we are still 
on the threshold of the evolution problem, and that the secret 
is largely tied up with that of vital phenomena in general. 
The very wide and positive differences of opinion which pre- 
vail are attributable largely to the unnatural divorce of the 
different branches of biology, to our extreme modern special- 
ization, to our lack of eclecticism in biology. We begin to 
grasp the magnitude of the problem only when side by side 
