94 INTRODUCTION. 



more or less probable assumptions. Upon the whole, how- 

 ever, it seems preferable to enter upon the study of the 

 actual facts of the science of Palaeontology, as far as may be, 

 unfettered by preconceptions and unpledged to theories ; while 

 we may, at the same time, safely accept the doctrine of evo- 

 lution, in the shape presented to us by the master-mind of 

 Darwin, as an invaluable, indeed an indispensable, working 

 hypothesis. 



