Dolbear.] 
200 
[Jan. 21, 
visible magnitude must be so complex that at any rate at present 
it would be quite a hopeless task to attempt to describe it, yet 
there does seem to be a good reason for having a well grounded 
conviction that in fact there must be such a field, and some sort 
of a mental picture of what it must be like. 
Physicists did not wait for the specific form of heat motions to 
be pointed out before they adopted in extenso the proposition 
that all the phenomena innst be due to motions. An obscure 
phenomenon did not cause them to hesitate, and why should it? 
Since the discovery of the mechanical equivalent of heat there 
has been no alternative that could be entertained a minute. It 
would not do for a man to say even that he did not know, for 
he had all the data there was. It has already been pointed out 
that such motions of matter as constitute sound, heat, magnetism 
and the rest, do all produce fields external to themselves and that 
within such fields other bodies are brought into similar states of 
position, or of motion, or both. Let this same principle be ap- 
plied to proptoplasm and cell structure. Imagine a cell with any 
degree of complexity, surrounded by material such as it is itself 
composed of and what should one look for to take place if not 
that the same kind of a structure should be reproduced? Where 
this happens we say that growth has taken place and it is attri- 
buted to life. As the new cell is similar to the old one that fur- 
nished the specific conditions for its development we say it has 
inherited its form and functions. 
The bearings of this upon the fundamental problems of biology 
are apparent. If the foregoing be true, heredity is explained 
as much as inductive magnetism is, and is no more mysterious. 
The cause of variation has been a subject much debated during 
the past few years and two schools of theory are still contending 
for acceptance ; one of them finding environment to be the chief 
factor, the other looking to supernaturalism for changes in 
organic evolution. Environment even in the hands of its friends 
is still a very vague and shadowy condition of things, but it is 
supposed to be altogether physical in its nature and to be subject 
to the ordinary laws of matter. As to supernaturalism, if con- 
sidered at all one is bound to admit its infinite possibilities, and 
also that an attempt at an explanation is absurd. On the other 
hand the possibilities of the mechanical combinations are infinite. 
Suppose that in such a complex molecule as protoplasm a sin- 
