CONTENTS 



PART I 



PAGE 



I. Introduction 3 



II. Technique 3 



III. Historical 5 



IV. Mouth-parts of the Embryo 6 



V. Mouth-parts of the Nymph 



Musculature 8 



Survey of the genera 12 



VI. Mouth-parts of the Subimago and Imago 



External metamorphosis 19 



Internal metamorphosis 19 



VII. Bibliography 23 



PART II 



Notes on the Biology of Mayflies of the Genus 



Baetis 40 



