THE DAWN OF THE EVOLUTIONARY 

 PERIOD. 



ERASMUS DARWIN. 



WE enter now upon the final phase of zoological science, 

 so far as we are here concerned namely, the phase in 

 which naturalists definitely accepted the principle of 

 ' Evolution ' as the key to biological problems of all 

 sorts, and more especially as explaining the much-vexed 

 question of the origin of ' species.' The two names which 

 are most intimately associated with the modern theory of 

 the origin of ' species ' by ' Descent with Modification ' 

 the ' Descendenz-theorie ' of the Germans are those of 

 Lamarck and of Charles Darwin. The former of these 

 wrote his 'Philosophic Zoologique' in the beginning of 

 the present century ; and the latter gave to the world his 

 epoch-making work on ' The Origin of Species by means 

 of Natural Selection' in the year 1859. The views put 

 forward in these two celebrated works will be shortly 

 sketched hereafter. In order, however, to trace with any 

 pretence to completeness the beginnings of the modern 

 theories as to the evolution of living beings, it is necessary 



