( IXY ) 
action of fire, carried to an extreme, carbonises organic matter, 
we should therefore eat our food raw. The irresponsible 
manipulation of biological hypotheses by pure speculators does 
no real or permanent injury to the cause of science, and may 
indirectly do good by directing public attention to the work 
which is being carried on. I rather think the absence of public 
sympathy, in connection with theoretical research in chemistry 
and physics, exerts a depressing influence ; the inventor of 
a new hypothesis in these subjects moves entirely in an 
atmosphere of his own creation, which even his colleagues 
seldom venture to penetrate. That biological speculations 
are more prone to such unauthorised treatment is no more a 
reason for refusing to speculate than the circumstance that 
generations of fact-collectors have wasted their time in 
amassing large stores of disconnected observations, which for 
want of system are practically of no avail to the scientific 
worker, is an argument in favour of repressing observation. 
It is possible to be quite as unscientific in the accumulation 
of facts as it is to become metaphysical by over-speculation ; 
there is as much danger in one direction as there is in. the 
other. Yet the most ardent advocate of the theoretical 
method has not taken it upon himself to declare that obser- 
vation must cease until he has explained all the facts at 
present available. This, however, is practically the position 
taken up by those who refuse to recognize that existing know- 
ledge is sufficient to enable considerable advance to be made 
by the legitimate use of the theoretical method. 
One other point demands consideration, in conclusion. If 
latitude for the exercise of speculation is to be allowed, 
where, it may be asked, is the line to be drawn ? How are 
we to distinguish between the cautious theoriser and the 
writer who permits himself "unbounded license?" These 
are questions to answer which requires nothing but an 
exercise of individual judgment. A sound speculation may 
emanate from the happy possessor of a philosophic mind 
although he may never have done any technical biological 
work. But this kind of speculator naturally fails to secure 
that hearing to which the practical worker is entitled. 
Although valuable generalisations may occasionally be given 
