THE BEGINNINGS OF LIFE. 599 



we have no evidence oi the origin of wild species in 

 this way. But this is not a case in which negative 

 evidence proves anything. We have never witnessed 

 the origin of a wild species by any process whatever • 

 and if a species were to come suddenly into being in 

 the wild state, as the Ancon sheep did under domesti- 

 cation, how could you ascertain the fact ? If the first 

 of a newly-begotten species were found, the fact of its 

 discovery would tell nothing about its origin. Natu- 

 ralists would register it as a very rare species, having 

 been only once met with, but they would have no 

 means of knowing whether it were the first or the last 

 of its race.' 



How is it possible, therefore, to gauge the amount of 

 this kind of change which takes place amongst higher 

 organisms, whereby new species may more or less 

 abruptly appear upon the scene ? Indeed, Mr. Darwin 

 himself says : — ' With such facts before us, we need feel 

 no surprise at the appearance of any modification in any 

 organic being.' Again, it must be almost certain that 

 in such cases we have to do with changes in molecular 

 constitution, similar in kind to those which amongst 

 simpler organisms sufficed to produce many of the 

 startling metamorphoses that have been recorded in 

 this work. 



We have endeavoured briefly to embody our own 

 views concerning the causes which determine and 



