CONTENTS XV 



PAGE 



2. Class I. Crustacea . ... 276 



a, The Crayfish Cambarus, 276 ; b, Crustacea in 

 General, 292. 



3. Class II. Onychophora 305 



4. Class III. Myriapoda 308 



5. Class IV. Insecta 312 



a, The Honey-bee, 312; b, The Anatomy and Physi- 

 ology of Insects in General, 328; c, General Survey 

 of the Orders of Insects, 336 ; d, The Economic Im- 

 portance of Insects, 370. 



6. Class V. Arachnida 371 



a, The Spiders, 371 ; b, Other Arachnida, 377. 



CHAPTER XIV 



PHYLUM CHORDATA : INTRODUCTION 386 



1. Subphylum I. ENTEROPNEUSTA 386 



2. Subphylum II. TUNICATA 389 



3. Subphylum III. CEPHALOCHORDA 393 



4. Subphylum IV. VERTEBRATA : INTRODUCTION . . 400 



CHAPTER XV 



SUBPHYLUM VERTEBRATA : Class I. Cyclostomata . . .414 



1. The Lamprey Petromyzon . . . . . .415 



2. Cyclostomata in General . . . . . . . 420 



CHAPTER XVI 



SUBPHYLUM VERTEBRATA : Class II. Elasmobranchii ] . . 422 



1. The Dogfish-Shark Squalus acanthias . . . . 422 



2. Elasmobranchs in General 428 



3. The Economic Importance of Elasmobranchs . . . 431 



CHAPTER XVII 



SUBPHYLUM VERTEBRATA : Class III. Pisces .... 432 



1. A Bony Fish The Perch 432 



2. An Abridged Classification of Living Fishes . . . 443 



