THE BEGINNINGS OF LIFE 



cates of " spontaneous generation " and their 

 antagonists is even narrower than appears from 

 the above statement of it. As practically con- 

 ducted, the dispute is confined to the ques- 

 tion whether certain particular low forms of life 

 — known as vibrios, bacteria, torulae, and mo- 

 nads — which appear in putrescence or in fer- 

 mentation, are produced by archebiosis, or are 

 propagated from germs conveyed in the atmos- 

 phere. 



If Dr. Bastian's position with reference to 

 this question is destined to become substanti- 

 ated, his work may perhaps mark an epoch in 

 biology hardly less important than that which 

 was inaugurated by Mr. Darwin's " Origin of 

 Species." Unfortunately, the kind of proof 

 which is needed for Dr. Bastian's main thesis 

 is much more difficult, both to obtain and to 

 estimate properly, than the kind of proof by 

 which the theory of natural selection has been 

 substantiated. In the latter case what was 

 needed was some principle of interpretation 

 which should account for the facts of the clas- 

 sification, embryology, morphology, and distri- 

 bution of plants and animals without appealing 

 to any other agencies than such as can be 

 proved to be actually in operation ; and it is 

 because the theory of natural selection furnishes 

 such a principle of interpretation that it has 

 met with such ready acceptance from the sci- 

 355 



