PREFACE 
HE aim of this book of short studies is to 
interest thoughtful readers in the multitudi- 
nous problems of animal life as they present them- 
selves to the modern biologist. Some of them deal 
with old problems which have reasserted themselves 
in new guise; others deal with new problems which 
recent research has brought into prominence. Most 
of them are confessedly appreciations of, and re- 
flections on, the investigations of other naturalists, 
and most of them were, to begin with, “ lectures ” 
to senior students of Natural History in this Uni- 
versity. It need hardly be said that the subjects 
chosen are only representative, and that the light 
thrown on them tends rather to an appreciation 
than to a solution of the problems involved. Nature 
so often tells us one secret in terms of another. 
The first ten studies deal with individual animals; 
the next six have to do with the web of life; the 
ten that follow raise problems of development and 
behavior—two subjects more intimately related 
than appears at first sight; the remaining fourteen 
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