GREAT STEPS IN ORGANIC EVOLUTION 911 



progress of spectroscopy beyond even telescopy, no one can set 

 limits to further extensions even of positive knowledge. It is mean- 

 time more attractive to speculate than to deny; so why not seek 

 further ways of searching for planets around other suns of this vast 

 stellar universe ? And returning to our own life-world, since it, after 

 all, makes what it can of its particular range of interaction with 

 solar and terrestrial environment, why not some such appropriate 

 and adaptive activities elsewhere? Even on this earth life is more 

 protean than we commonly realise; witness those strange bacterial 

 forms which vegetate and synthetise in ways chemically quite out- 

 side those of others, and still more of our ordinary plant-world. 

 And again, if our human thought ranges out into the Universe, 

 can such thought be all there is? Let us at least keep our thought 

 open. Who knows what may befall? 



