life: its nature, origin, and maintenance SCHAFER. 603 



Various eminent scientific men have even supposed that life has not 

 actually originated upon our globe, but has been brought to it from 

 another planet or from another stellar system. Some of my audience 

 may still remember the controversy that was excited when the theory 

 of the origin of terrestrial Hfe by the intermediation of a meteorite 

 was propounded by Sir William Thomson in his presidential address 

 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 60,000,000 years for a meteorite to travel from the 

 nearest stellar system to our earth, and it is inconceivable that any 

 kind of hfe could be maintained during such a period. Even from 

 the nearest planet 150 years would be necessary, and the heating of 

 the meteorite in passing through our atmosphere and at its impact 

 wdth the earth would, in all probabihty, destroy any hfe which might 

 have existed within it. A cognate theory, that of cosmic imnsfermia, 

 assumes that hfe may exist and may have existed indefiuitel}^ in 

 cosmic dust in the interstellar spaces (Richter, 1865; Cohn, 1872), 

 and may with this dust faU slowty to the earth without undergoing 

 the heating wliich is experienced by a meteorite. Arrhenius,^ who 

 adopts this theory, states that if h^'ing germs were carried through the 

 ether by luminous and other radiations, the time necessary for their 

 transportation from our globe to the nearest steUar system would be 

 only 9,000 years, and to Mars only 20 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 inaccessible corner of the uni- 

 verse and leaves us in the unsatisfactory position of affirming not 

 oiJy 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 — which it is to be hoped is not true.^ Knowing what we 

 know, and believing what we believe, as to the part played by evo- 

 lution in the development of terrestrial matter, we are, I think (with- 

 out denying the possibility of the existence ol life in other parts of 

 the universe*), justified in regarding these cosmic theories as inlier- 

 ently improbable — at least in comparison with the solution of the 

 problem which the evolutionary liypotliesis offei's.'^ 



1 First suggested, according to Dastre, by de Salles-Guyon (Dastre, op. cit., p. 252). The theory received 



the support of Ilclmholtz. 



5 Worlds in the Making, transl. by H. Boms, Chap. VIU, p. 221, 1908. 



' " The History of science shows how dangerous it is to brush aside mysteries— i. c., unsolved problems— 

 and to interpose the barrier placarded 'eternal— no thoroughfare.' "— R. Meldola, Herbert Spencer J>ccture, 

 1910. 



< Some authorities, such as Errera, contend with much probability, that the conditions in iTitcrstcUar 

 space are such that life, as we understand it, could not possibly exist there. 



•' As Ver^N'om points out, such theories would equally apply to the orifrin of any other chemical combi- 

 nation, whether inorganic or organic, which is met with on our globe, so that they lead directly to absurd 

 conclusions.— AUgemeine Physiologie, 1911. 



