INTRODUCTORY 
S 
the problem as to have been able, as it were, so 
to engineer circumstances that the Cuckoo has, 
over and over again, revealed her secret for 
our edification and instruction. Herein lies the 
uniqueness of our methods, for it is scarcely an 
exaggeration to say that we have made our Cuckoos 
show us what we want to see, whereas all previous 
students have had to rely solely upon luck, which, 
where the Cuckoo is concerned, is well-nigh 
useless. 
Amongst those previous students to whom I 
just have referred, the place of honour is taken by 
Dr. Eugene Rey, of Leipzig, who in 1892 published 
a record * of his investigations and researches in 
Cuckoo problems extending over a number of years. 
The results which he achieved appear, nevertheless, 
to be almost unknown to most of our field-naturalists, 
as indeed I must confess they were to myself until 
after I had made many of the observations recorded 
in this volume. So interesting is his book that I 
have recently had it translated into English, and 
have been thus able to introduce it to many practical 
ornithologists. 
* Altes und Neues aus dem Haushalte des Kuckucks. 
(Zoologische Vortraege , herausgegeben von W. Marshall, Heft 1 1 .) 
Leipzig, 1892. 
