PREFACE ix 



tions. My investigation proved it to be so, a rotten 

 tenement tottering in its every joint a ship tumbling 

 helplessly on the brine, leaking at every plank. 



In the chapter entitled " Natural Selection " I have 

 stated my belief in the doctrine of Evolution, accord- 

 ing to which the higher forms of life have been evolved 

 from lower forms, and I have accepted the received 

 opinion that the higher vertebrates were once fish 

 forms disporting in the tepid waters of an earlier 

 world. 



Short as the time is that has elapsed between the 

 body of this work having passed through the press 

 and the writing of this Preface, I have found strong 

 and to myself incontrovertible reasons for reconsider- 

 ing my views in regard to the doctrine of a material 

 evolution from lower to higher forms of life. What 

 these reasons are which have constrained me, a life- 

 long evolutionist, now touching upon man's allotted 

 span of life, to alter my previous convictions, I will 

 state in terms as concise as possible with a due 

 regard to necessary clearness. 



The only evolutionary power of Nature known to 

 true Science is that which is exerted by its changed 

 environment, when by any compelling cause a group 

 of animals (for I am dealing with animated Nature 

 only) is forced to migrate and come under new 

 external conditions. This is the principle of Lamarck, 

 according to which the new material environment, 

 from its every several feature, from the form and 

 configuration of the country, from the nature, colour, 



