"THROUGH THE EYE" SERIES EVOLUTION "THROUGH THE EYE" SERIES _THE FIRST TWO VOLUMES_ EVOLUTION. By J. A. S. WATSON, B.Sc. THE CIVILIZATION OF THE ANCIENT EGYPTIANS. By A. BOTHWELL GOSSE. _Other Volumes in Preparation_ [Illustration: FIG. 1.--Tree illustrating the probable course of animal evolution.] EVOLUTION BY J. A. S. WATSON, B.Sc. [Illustration: THROUGH THE · EYE] _Published by_ T. C. & E. C. JACK, LTD. 35 & 36 PATERNOSTER ROW, LONDON, E.C. AND AT EDINBURGH _Printed in Great Britain_ CONTENTS CHAPTER I PAGE THE EVIDENCE FOR EVOLUTION 1 CHAPTER II UNICELLULAR AND MULTICELLULAR ANIMALS 23 CHAPTER III THE WORMS AND SOME OF THEIR POSTERITY 58 CHAPTER IV THE EARLY VERTEBRATES AND THE FISHES 79 CHAPTER V THE CONQUEST OF THE LAND 104 CHAPTER VI THE MAMMALS AND MAN 123 For many of the illustrations the Publishers are indebted to the Deutsche Verlags-Anstalt (from Günther's _Vom Urtier zum Menschen_) and Herr Wilhelm Engelmann (from Haeckel's _Anthropogenie_). Acknowledgment is also made to Messrs. Watts & Co., London, the Publishers of the English Edition of Haeckel's _Anthropogenie_, entitled _The Evolution of Man_. EVOLUTION CHAPTER I THE EVIDENCE FOR EVOLUTION The idea of Evolution is an old one. It is older than the Darwinian hypothesis; it is older than Lamarck, who published his particular theory in 1809, the year that Darwin was born; it is older than Buffon or Kant. In a fairly definite form it is as old as Aristotle. The Evolution idea has thus itself evolved, and is the product of many centuries of thought. Yet it was only the last generation that began to give the idea serious consideration, and it is perhaps only the present that has granted it any general measure of acceptance; and it was Darwin who wrought this change, who raised the conception of Evolution from the status of a vague speculative idea to that of a well-grounded theory, which appeals to the majority of educated minds as satisfactory and reasonable.