IT has been my privilege to work for some three years with Mr Unwin as my colleague at Bootham School. Inhabiting a study next to his lecture room I have heard fragments of many of these lessons and I know for myself how keen has been the interest evoked, how eager the little crowd round the table afterwards. It has been a revelation to me to see how standards of knowledge appropriate to a university professor have captured the confidence of the youngest class of school- boys. Now that even the kindergarten dabbles in pond life it is necessary to appeal for far higher standards of thoroughness if the same topics are still to rivet attention at an older age.
This book is really about environment, natural selection and evolution, even if such long words are avoided in the text. The lessons have been test.ed in detail, and information about apparatus and materials will be useful both to teacher and pupil in arranging for practical work.
Mr Unwin has had great experience as a teacher, having been for four years Demonstrator in Zoology at Leeds University, Science Master at Ackworth, Bootham and Leighton Park Schools, master of a preparatory school, as well as lecturer on Nature Study to adult audiences of teachers and others. 'He is also his own artist and the illustrations in this book, almost without exception, are from his pen or camera.

EDITOR'S PREFACE vii

INTRODUCTION xiii

I. How TO OBTAIN SPECIMENS 1

II. WHAT IS AN INSECT? 9

III. THE PROBLEMS STATED 18

IV. BREATHING. WATER-BEETLES AND WATER-BOATMEN 21

V. SURFACE-FILM BREATHING 26

VI. DIVING-TUBES AND A DIVING-BELL 35

VII. A NEW INVENTION 42

VIII. LOCOMOTION 55

IX. THE ESCAPE FROM THE WATER 74

X. LIFE STORIES. FROM EGO TO IMAGO 87

APPENDIXES 106

INDEX 118

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