384 GREAT STEPS IN ORGANIC EVOLUTION 



was a time, therefore, when living organisms began to be 

 upon the earth. 



Whether germs of living organisms reached terrestrial 

 shores from elsewhere, borne in the crevices of a meteorite 

 or wafted by light waves amid cosmic dust, or whether 

 living organisms may have evolved from not-living material, 

 e.g., from some colloidal carbonaceous slime in which fer- 

 ments were operative, we do not know, l^o hypothesis of 

 abiogenesis (i.e., of the origin of the living from the not- 

 living) has yet been suggested that can be accepted with 

 easy-going satisfaction. Whether we start with an inorganic 

 colloid able to utilise solar energy, or with formaldehyde 

 generated by lightning flashes through moist air, or with 

 the cyanogen radicle formed in incandescent materials, diffi- 

 culties abound. It is not of much avail to point to the 

 achievements of the synthetic chemist unless we can indicate 

 in Inorganic ISTature some analogous agency able to pick 

 and choose, combine and eliminate. On the other hand, one 

 is not inclined to lay much stress on the fact that there 

 has not been as yet effected in the chemical laboratories 

 any synthesis of natural proteins, the substances which 

 always form an important part of the physical basis of 

 life; for who would have suspected a few years ago that 

 we should now be using artificially compounded indigo and 

 salicylic acid ? More important is it to remember that there 

 is not to be found in natural conditions anything like living 

 matter (or protoplasm) except as organised in the form of 

 organisms or pieces of organisms ; that we do not know of 

 a ^ living substance ' as we know of, say, albumen ; that the 

 problem is the origin of organisms. 



As regards the origin of protoplasm, " the physical basis 

 of life ", as Huxley called it, there is not at present much 



