18 tEESIDEl^TIAL ADDfiESS, 



germs, though it is beyond our power as yet to discriminate them 

 in their earliest stage, become more and more differentiated as 

 they advance. And it has always appeared to me that this ad- 

 mitted fact gives an as yet unrefuted answer to the claim of 

 identity, and rather proves that from the very earliest stage there 

 must be a distinction and a difference, though our power and re- 

 sources, whether chemical or microscopic, have not yet been able 

 to detect the difference at that early stage. The growth of the 

 germ is one of evolution or development. But do all living forms 

 proceed from germs or organized matter, without exception, 

 which has belonged to parents ; or is there anything like spon- 

 taneous generation or the evolution of life from non-life? So 

 far as the keenest research has hitherto reached, we may deci- 

 dedly affirm, pace Dr. Bastian, supported by such authorities as 

 Huxley and Tyndal, that there is not a scintilla of evidence to 

 support the theory. "We must beware of confounding knowledge 

 and opinion. Evolution is doubtless one of the processes by 

 which modifications of the forms of pre-existing life are brought 

 about, but more than this I submit we cannot as scientific 

 students state to be proved. Let us keep knoAvledge distinct 

 from opinion, from theory, from subjective impressions. Still 

 the limits of knowledge are at all times expanding, and the 

 boundaries of the known and the unknown are never rigid or 

 permanently fixed. Our ignorance consists partly in ignorance 

 of actual facts, and partly also in ignorance of the possible range 

 of ascertainable fact. If we could lay down beforehand the pre- 

 cise limits of possible knowledge, the problem of physical science 

 would be half-solved already. But the question to which the 

 scientific explorer has often to address himself is not merely 

 whether he is able to solve this or that problem, but whether 

 he can so far unravel the tangled threads of the matters with 

 which he has to deal, as to weave them into a problem at all. 

 He is not a candidate at the examination table, with a set of 

 questions to which he might give answers, and which can all 

 be solved. He is rather the look-out at the mast head, peering 

 through a cloudy atmosphere, and endeavouring to trace the out- 

 line of the coast as best he can j trying to direct his vessel where 



