chap, i.] INTRODUCTION. 9 



fessor Ernst Haeckel, 1 Dr. Fritz Midler, 2 and others of 

 their enthusiastic disciples and commentators. I do 

 not think that I am speaking too strongly when I say 

 that there is now scarcely a single competent general 

 naturalist who is not prepared to accept some form 

 of the doctrine of evolution. 



There is, no doubt, very great difficulty in the 

 minds of many of us in conceiving that, commenc- 

 ing from the simplest living being, the present state 

 of things in the organic world has been produced 

 solely by the combined action of < atavism,' the ten- 

 dency of offspring to resemble their parents closely ; 

 and 'variation,' the tendency of offspring to differ 

 individually from their parents within very narrow 

 limits : and many are inclined to believe that some 

 other law than the ' survival of the fittest ' must 

 regulate the existing marvellous system of extreme 

 and yet harmonious modification. Still it must be 

 admitted that variation is a vera causa, capable, 

 within a limited period, under favourable circum- 

 stances, of converting one species into what, accord- 

 ing to our present ideas, we should be forced to 

 recognize as a different species. And such being the 

 case, it is, perhaps, conceivable that during the lapse 

 of a period of time — still infinitely shorter than 

 eternity — variation may have produced the entire 

 result. 



1 Generelle Morphologie der Organisnien. Allgemeine Grundziige 

 der organischen Fornien-Wissenschaft mechanisch begriindet durch 

 die von Charles Darwin reformirte Descendenz-Theorie. Von Ernst 

 Haeckel. Berlin, 1866. — Natiirliche Schopfungsgeschichte. Von Dr. 

 Ernst Haeckel, Professor an der TJniversitat Jena. Berlin, 1870. 



2 Fiir Darwin. Von Dr. Fritz Miiller. Leipzig, 1864. Translated 

 from the German by W. S. Dallas, F.L.S. . London, 1869. 



