September 6, 1912] 



SCIENCE 



295 



—is possible at the present day — and for 

 my own part I see no reason to doubt it — 

 a boiled infusion of organic matter — and 

 still less of inorganic matter — is the last 

 place in which to look for it. Our mistrust 

 of such evidence as has yet been brought 

 forward need not, however, preclude us 

 from admitting the possibility of the for- 

 mation of living from non-living substance. 



Setting aside, as devoid of scientific 

 foundation, the idea of immediate super- 

 natural intervention in the first production 

 of life, we are not only justified in be- 

 lieving, but compelled to believe, that 

 living matter must have owed its origin to 

 causes similar in character to those which 

 have been instrumental in producing all 

 other forms of matter in the universe; in 

 other words, to a process of gradual evolu- 

 tion. But it has been customary of late 

 amongst biologists to shelve the investiga- 

 tion of the mode of origin of life by evolu- 

 tion from non-living matter by relegating 

 its solution to some former condition of 

 the earth's history, when, it is assumed, 

 opportunities were accidentally favorable 

 for the passage of inanimate matter into 

 animate; such opportunities, it is also as- 

 sumed, having never since recurred and 

 being never likely to recur. 



Various eminent scientific men have even 

 supposed that life has not actually orig- 

 inated upon our globe, but has been 

 brought to it from another planet or from 

 another stellar system. Some of my audi- 

 ence may still remember the controversy 

 that was excited when the theory of the 

 origin of terrestrial life by the intermedia- 

 tion of a meteorite was propounded by Sir 

 William Thomson in his presidential ad- 

 dress at the meeting of this association in 

 Edinburgh in 1871. To this "meteorite" 

 theory the apparently fatal objection was 

 raised that it would take some sixty million 

 years for a meteorite to travel from the 



nearest stellar system to our earth, and it 

 is inconceivable that any kind of life could 

 be maintained during such a period. Even 

 from the nearest planet one hundred and 

 fifty years would be necessary, and the 

 heating of the meteorite in passing through 

 our atmosphere and at its impact with the 

 earth would, in all probability, destroy any 

 life which might have existed within it. A 

 cognate theory, that of cosmic panspermia, 

 assumes that life may exist and may have 

 existed indefinitely in cosmic dust in the 

 interstellar spaces (Richter, 1865; Cohn, 

 1872), and may with this dust fall slowly 

 to the earth without undergoing the heat- 

 ing which is experienced by a meteorite. 

 Arrhenius, who adopts this theory, states 

 that if living germs were carried through 

 the ether by luminous and other radiations 

 the time necessary for their transportation 

 from our globe to the nearest stellar system 

 would be only nine thousand years, and to 

 Mars only twenty days ! 



But the acceptance of such theories of 

 the arrival of life on the earth does not 

 bring us any nearer to a conception of its 

 actual mode of origin; on the contrary it 

 merely serves to banish the investigation 

 of the question to some conveniently inac- 

 cessible corner of the universe and leaves 

 us in the unsatisfactory position of affirm- 

 ing not only that we have no knowledge 

 as to the mode of origin of life — which is 

 unfortunately true — ^but that we never can 

 acquire such knowledge — ^whieh it is to be 

 hoped is not true. Knowing what we 

 know, and believing what we believe, as to 

 the part played by evolution in the devel- 

 opment of terrestrial matter, we are, I 

 think (without denying the possibility of 

 the existence of life in other parts of the 

 universe), justified in regarding these cos- 

 mic theories as inherently improbable — at 

 least in comparison with the solution of the 



