PREFACE. 



I WISH that dedications were still in vogue, so that 

 these pages could be inscribed to all those many friends 

 whose unfailing kindness and courtesy made my visit to 

 the United States so pleasant, when the substance of this 

 volume was delivered as a Lowell Course at Boston, and 

 as lectures in New York, Chicago, and other university 

 centres, during the early part of this year. 



The reader will doubtless be glad to learn that further 

 observations — and they are much needed — on habit and 

 instinct will probably form part of Prof. Whitman's work 

 at an experimental station in connection with the Bio- 

 logical Department of Chicago University. Similar 

 observations might also be prosecuted with advantage 

 in some of our own zoological gardens, as was the earnest 

 wish of George Romanes, to whose influence and encourage- 

 ment I am, like many others, so deeply indebted. 



A few passages from the Fortnightly Review, Nature, 

 Natural Sciejice, the Monist, and the Humanitarian, may 

 perhaps be recognized. Much of the chapter on Modifica- 

 tion has appeared by request in Science. 



My best thanks are due to Mr. F. Howard Collins for 

 many valuable suggestions. 



C. Ll. M. 



Bristol, October, 1896. 



