VERTEBRATA: LITERATURE. 459 



the Reptiles and the Birds, two classes which are certainly 

 very nearly allied to one another. 



By Professor Huxley the Vertebrata are divided into the 

 following three primary sections : 



I. ICHTHYOPSIDA. This section comprises the Fishes and 

 the Amphibians, and is characterised by the presence at some 

 period of life of gills or branchiae, the absence of an amnion, 

 the absence or rudimentary condition of the allantois, and the 

 possession of nucleated red blood-corpuscles. 



II. SAUROPSIDA. This section comprises the Birds and the 

 Reptiles, and is characterised by the constant absence of gills, 

 the possession of an amnion and allantois, the articulation of 

 the skull with the vertebral column by a single occipital con- 

 dyle ; the composition of each ramus of the lower jaw of seve- 

 ral pieces, and the articulation of the lower jaw with the skull 

 by the intervention of an " os quadratum ; " and, lastly, the 

 possession of nucleated red blood-corpuscles. 



III. MAMMALIA. This section includes the single class of 

 the Mammals, and agrees with the preceding in never possess- 

 ing gills, and in having an amnion and allantois. The Mam- 

 malia t however, differ from the Sauropsida in the fact that the 

 skull articulates with the vertebral column by two occipital 

 condyles ; each ramus of the lower jaw is simple, composed of 

 a single piece, and the lower jaw is united with the temporal 

 (squamosal) element of the skull, and is not articulated to a 

 quadrate bone. There are special glands the mammary 

 glands for the nourishment of the young for a longer or 

 shorter period after birth, and the red blood-corpuscles are 

 non-nucleated. 



LITERATURE. 



1. "Comparative Anatomy and Physiology of Vertebrates." Owen. 



1866-68. 



2. " Manual of the Anatomy of Vertebrated Animals." Huxley. 1872. 



3. " Principles of Comparative Physiology. " W. B. Carpenter. 



4. " Forms of Animal Life. " Rolleston. 1870. 



5. "General Outline of the Organisation of the Animal Kingdom." 



Rymer Jones. 1871. 



6. "Handbook of Zoology." Van der Hoeven. Trans, by Dr W. 



Clarke. 1856-58. 



7. ' ' Manual of Comparative Anatomy. " Blumenbach. Trans, by 



Laurence. 1827. 



8. " Comparative Anatomy of Vertebrate Animals." Wagner. Trans. 



by Tulk. 1845. 



9. " Grundriss der Vergleichenden Anatomic." Gegenbaur. 1874. 



10. " Le Regne Animal distribue d'apres son organisation." Cuvier. 



11. " Le9ons d'anatomie comparee." Cuvier. 



