HEREDITY AND EVOLUTION. 531 



fall back on those tangible manifestations which are to be studied only 

 by field observation and experimental breeding. 



The breeding-pen is to us what the test-tube is to the chemist — an 

 instrument whereby we examine the nature of our organisms and de- 

 termine empirically what for brevity I may call their genetic proper- 

 ties. As unorganized substances have their definite properties, so have 

 the several species and varieties which form the materials of our ex- 

 periments. Every attempt to determine these definite properties con- 

 tributes immediately to the solution of that problem of problems, the 

 physical constitution of a living organism. In those morphological 

 studies which I suppose most of us have in our time pursued, we sought 

 inspiration from the belief that in the examination of present nor- 

 malities we were tracing the past, the phylogenetic order of our types, 

 the history — as we conceived — of evolution. In the work which I am 

 now pressing upon your notice we may claim to be dealing not only 

 with the present and the past, but with the future also. 



On such an occasion as this it is impossible to present to you in 

 detail the experiments — some exceedingly complex — already made in 

 response to this newer inspiration. I must speak of results, not of 

 methods. At a later meeting, moreover, there will be opportunities of 

 exhibiting practically to those interested some of the more palpable 

 illustrations. It is also impossible to-day to make use of the symbolic 

 demonstrations by which the lines of analysis must be represented. 

 The time can not be far distant when ordinary Mendelian formulae 

 will be mere as in prcesenti to a biological audience. Nearly five years 

 have passed since this extraordinary rediscovery was made known to 

 the scientific world by the practically simultaneous papers of De Vries, 

 Correns and Tschermak, not to speak of thirty-five years of neglect 

 endured before. Yet a phenomenon comparable in significance with 

 any that biological science has revealed remains the intellectual pos- 

 session of specialists. We still speak sometimes of Mendel's hypothe- 

 sis or theory, but in truth the terms have no strict application. It is 

 no theory that water is made up of hydrogen and oxygen, though we 

 can not watch the atoms unite, and it is no theory that the blue Anda- 

 lusian fowl I produce was made by the meeting of germ-cells bearing 

 respectively black and a peculiar white. Both are incontrovertible 

 facts deduced from observation. The two facts have this in common 

 also, that their perception gives us a glimpse into that hidden order 

 out of which the seeming disorder of our world is built. If I refer to 

 Mendelian ' theory,' therefore, in the words with which Bacon intro- 

 duced his Great Instauration, ' I entreat men to believe that it is not 

 an opinion to be held, but a work to be done; and to be well assured 

 that I am laboring to lay the foundation, not of any sect or doctrine, 

 but of human utility and power.' 



