6 GENETICS 



matter, and the one thing that must be explained is 

 not the origin of Hfe, but of the non-Hving, no one 

 can say. Leaving aside the first speculation as un- 

 tenable and the third as irrational, since it jars so 

 sadly with what astronomers tell us of the probable 

 evolution of worlds, the theory of spontaneous gener- 

 ation seems to be the last resort to which to turn. 



In prescientific days this idea of spontaneous 

 generation presented no great difficulties to our 

 imaginative and credulous ancestors. John Milton, 

 with the assurance of an eye-witness, thus described 

 the inorganic origin of a lion : — 



*' The grassy clods now calved ; now half appears 

 The tawny lion, pawing to get free 

 His hinder parts — then springs as broke from bonds, 

 And rampant shakes his brindled mane." 



(" Paradise Lost," Book VII, line 543.) 



Ovid also in his ''Metamorphoses," not to mention a 

 more familiar instance, easily succeeded in creating 

 mankind from the humble stones tossed by the 

 juggling hands of Deucalion and Pyrrha. 



Although under former conditions on the earth 

 it might have been possible for life to have originated 

 spontaneously, and although it may yet be possible 

 to produce life from inorganic materials in the labora- 

 tory or elsewhere, the exhaustive work of Pasteur, 

 Tyndall and others effectually demonstrated a genera- 

 tion ago that to-day living matter always arises from 

 preceding living matter and this conclusion is gener- 

 ally accepted as an axiom in genetics. 



