I. SUBKINGDOM VERTEBRATA. 



^g.z^ General Characteristics,— The Ver- 



tebrates are usually distinguished by a 

 chain of small bones (vertebrae) to which 

 the other parts of the skeleton are at- 

 tached.* Certain modifications in the 

 structure of these animals separate them 

 into Classes, according to the following 

 table : 



<s^i 



SUBEINGDOH. 



GQ 



'Vivipar( 



(producing i 

 living [ 

 young). [ 



Suckle theie young ; lungs ; 

 respiration simple; blood 

 warm ; o1rc0lation double 

 AND complete; heart four- 



CHAMBERED. 



ReBplration double ; ■ 



blood warm ; 



circulation double 



and complete ; 



heart 



four-chambered. J 



Respiration 



aerial ; 

 WITH lungs. 



Respiration 



AQUATIO when 

 YOUNG, AERIAL 

 WHEN MATURE, 

 OR WITH BOTH 

 LUNGS AND GILLS 

 AQUATIC AND 

 AERIAL. 



Respiration 

 aquatio, with 



GILLS. 



Respiration simple ; ■ 

 blood cold ; 

 circulation 

 incomplete ; 

 heart mostly three- 

 chambered ; 

 skull one occipital 

 condyle 

 (see Glossary). 



Respiration simple 



when mature ; 



blood cold ; 



circulation incom- 



heart three- 

 chambered ; 

 skull two occipital 

 condyles. 



MammaiiOt 



<]birds\. 



S^aHdh 



■ Amphibia. 



{Blood cold ; 1 

 heart mostly l 

 two-chambered. J 



PiSCM 



{jiehesU 



* For a description of the vertebral colnmn, and the advantages of its peculiar 

 torm, see ** Fourteen Weeks in Physiology," page 27, et seq. 



