txii GENERAL INDEX. 



Page 

 Simplification of the vertebral column as it approaches the caudal 



region 615 



Composition of the cranial portion of the spinal column . . . 615 



Cranium divisible into four vertebrae 615 



Composition of occipital vertebra . . . . . u . , . . . 616 



parietal vertebra . . ., r . ' . * i ' . "-,. -*:i ;-. 616 



frontal vertebra 616 



nasal vertebra 616 



Composition of typical vertebrate skeleton 616 



General view of the nervous system of the Vertebrate . . . . 618 



Brain 618 



Spinal medulla 618 



Sensitive and motor columns of the spinal cord 618 



Origin of spinal nerves 618 



Their compound structure .... *W:-*' 618 



Sympathetic system - v 619 



Senses of the Vertebrate . . . *>?.'. 1-4^ - v v- .:..-.-v *v ;- 619 



Additions to alimentary system 619 



Pancreas .v\. v i; *.,.. 619 



l ic portal system 619 



. 620 



nphatics and lacteal vessels 620 



Circulatory and respiratory systems 620 



Tegumentery system 620 



Instincts and affections 621 



CHAPTER XXVI. 



PISCES FISHES. 



FISHES General survey of the class ; 621 



Transitional condition of the skeleton in Myxine and the Lamprey 622 



Amphioxus 622 



Rudimentary condition of osseous system 623 



Entire absence of cranial cavity 623 



Structure of the mouth of Amphioxus 623 



Arrangement of branchial chamber 624 



Digestive system of Amphioxus 624 



Reproductive organs 625 



Circulatory system of Amphioxus 625 



" Arterial heart " 625 



" Bulbs " of the branchial arteries 625 



" Aortic arch " performing the functions of a systemic heart . . 626 



" Heart of the vena porta " 626 



" Heart of the vena cava " ' : ', . ... 626 



Mechanism of the circulation in Amphioxus 626 



Apparent absence of brain 626 



Gradations in the structure of the vertebral column of fishes . . 627 



Structure of the bodies of the vertebrae in fishes 628 



Vertebral processes 628 



Structure of caudal vertebra 628 



Ribs 628 



Structure of the azygos fins of fishes 630 



Interspinous bones 630 



Fin-rays 630 



Articulation between fin-rays and interspinous bones . . . . . 631 



Composition of the skull of osseous fishes 631 



Cranium . .. v . 631 



composed of twenty-six bones 632 



Principal frontal 632 



Anterior frontal . . 632 



Posterior frontal ". *"Y '...*". . 632 



