CONTENT*. xiii 



PACK 



G. ORGANS OF RESPIRATION 



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 



ABDOMLSAi FORES 265 



Bibliography 267 



H. ORGANS OF CIRCULATION 268 



VASCULAR SYSTEM) 268 



Development of the Heart and Blood- Vessels 268 



The Fcetal 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. URINOGENITAL ORGANS .296 



Development 296 



URINARY ORGANS 302 



of Fishes and Dipnoans 302 



of Amphibians 304 



of Reptiles and Birds 307 



of Mammals 308 



