( Ixiii ) 
will, as Faraday said, encourage themselves by a little more 
speculation. Judging from the part played by this method 
in the development of modern science, it is perhaps not 
going too far to say that it is better to have speculated 
erroneously than never to have speculated at all. Illustra- 
tions might be adduced showing that erroneous theories have 
often done good service to science, and that for this reason 
they have been temporarily retained, even when recognized 
as inadequate to meet the growing body of new evidence. 
This was the case, for example, with the old " fluid " theory 
of electricity. So also the "corpuscular" theory of light 
enabled Newton to develop optical science to a remarkable 
extent, although this theory is now among what Dr. Hicks 
calls the wreckage." 
Another source of danger in biological speculation to which 
I am also alive, is that we have the public eye upon us to an 
extent that is not experienced in other departments of science. 
I am bound to confess that I never could quite make out why 
this should be the case. It is possible to speculate about the 
constitution of matter, the degradation of energy, the age of 
the solar system, and other great problems of the universe, 
with any degree of dogmatism without exciting public dis- 
cussion. But as soon as ever an effort is made to explain 
something in the living world, no matter how modestly, the 
speculator is forthwith treated as though he had thrown down 
a public challenge. Perhaps it is for this reason that biology 
is more subject to unauthorised and unscientific intrusion ; 
because it gives opportunity for the pure litterateur to pose as a 
theorist. The speculations of the physicist or chemist are, 
moreover, generally expressed in a symbolical language which 
is not understood by the public at large, and their ideas, how- 
ever revolutionary, thus escape newspaper and magazine 
notoriety. As far as my reading extends, I am inclined to 
believe that even in the case of the purely literary treatment 
of biological problems by writers who are not experts, the 
danger of overweighting the science with hypothesis is much 
exaggerated. Writers of this class are often capable of taking 
a wider and more philosophic grasp of a problem than a pure 
specialist, and ideas of lasting value have sometimes emanated 
