CONTENTS. xiii 



I'ACiE 



G. ORGANS OF RESPIRATION .... 245 



I. GILLS 245 



of Amphioxus 246 



of Cyclostomi . . - 246 



of Fishes 248 



of Dipnoi 250 



of Amphibia 250 



II. AIR-BLADDER AND LUNGS 251 



1. THE AIR-BLADDER 251 



2. THE LUNGS 252 



Air-Passages 253 



of Amphibians 253 



of Reptiles 254 



of Birds 255 



of Mammals 255 



The Lungs in a more Restricted Sense 257 



The Lungs of Dipnoi 257 



of Amphibia 257 



of Reptiles 258 



The Lungs and Air-Sacs of Birds 259 



The Lungs of Mammals 263 



ABDOMINAL PORES 265 



Bibliography 267 



H. ORGANS OF CIRCULATION 268 



(VASCULAR SYSTEM) 268 



Development of the Heart and Blood- Vessels 268 



The Foetal Circulation 270 



The Heart and its Vessels . ' 277 



of Fishes 277 



of Dipnoi 280 



of Amphibia 281 



of Reptiles . 284 



of Birds and Mammals 286 



Arterial System 288 



Venous System 291 



Retia Mirabilia 292 



Lymphatic System 292 



Bibliography 294 



I. TTRINOGENITAL ORGANS 296 



Development 296 



URINARY ORGANS . 302 



of Fishes and Dipnoans 302 



of Amphibians 304 



of Reptiles and Birds 307 



of Mammals .... 308 



