INTRODUCTION 



lectures, Agassiz still dominated the teaching 

 current upon these issues at Harvard. The 

 Darwinian theory, equally with Spencer's phi- 

 losophy, was on trial before the public. Ele- 

 mentary objections and misunderstandings, as 

 well as the far more weighty problems of the 

 new theories, had to be considered and ex- 

 plained. Moreover, the now obsolete contro- 

 versy concerning " spontaneous generation " 

 was, when Fiske published these volumes, still 

 prominent in the literature of the day. The 

 more modern researches of the bacteriologists 

 were in their infancy. The special question as 

 to the " factors of organic evolution " had 

 not yet become disengaged from its natural 

 confusion in the minds of readers with the 

 more general question as to whether organic 

 forms were the product of special creation or 

 not. Even the importance of the difference 

 between the Spencerian and the Darwinian ten- 

 dencies in the explanation of these factors of 

 organic evolution had not yet been as much 

 emphasized as the controversy between the 

 " Neo-Lamarckians " and their opponents has 

 since emphasized it. In short, more than a 

 quarter of a century of restless scientific pro- 

 gress lies between these brilliant chapters of 

 Fiske and the present state of opinion and of 

 knowledge concerning evolutionary theory. 

 Ixii 



