156 ZOOLOGICAL PHILOSOPHY 



VERTEBRATE ANIMALS. 



They have a vertebral column consisting of a number of short articu- 

 lated bones following one another in succession. This column serves 

 to support their body, it is the basis of their skeleton, constitutes a 

 sheath for their spinal cord, and terminates anteriorly in a bony case 

 containing the brain. 



FIFTH STAGE OF ORGANISATION. 



Nerves terminating in a spinal cord and a brain which does not 

 fill up the cavity of the cranium ; heart with one ventricle and cold 

 blood. 



(Fishes and Reptiles.) 



FISHES. 



(Class XL of the Animal Kingdom.) 



Oviparous vertebrate animals with cold blood ; living in water, breathing 

 by gills, covered with a shin either scaly or almost naked and slimy, and 

 having for their locomotive movements only membranous fins supported 

 by a bony or cartilaginous framework. 



Observations. 



The organisation of the fishes is much more perfect than that of the 

 molluscs and animals of the anterior classes, since they are the first 

 animals to have a vertebral column, the rudiments of a skeleton, a 

 spinal cord and a cranium enclosing the brain. They are also the first 

 in which the muscular system derives its support from internal 

 parts. 



Nevertheless their respiratory organs are still analogous to those of 

 the molluscs, cirrhipedes, annehds and crustaceans ; and Kke all the 

 animals of the preceding classes, they are still without a voice and have 

 no eyelids. 



The shape of their body is adapted to their necessity for swi mmi ng ; 

 but they maintain the symmetrical shape of paired parts started in the 

 insects ; lastly, among them as among the animals of the three follow- 

 ing classes, the type of articulations is altogether internal, and only 

 occurs in the parts of their skeleton. 



N.B. — ^In the preparation of the tables of vertebrate animals I 

 have used M. Dumeril's work entitled Zoologie Analytique, and I 

 have permitted myself to make but few changes in his arrangement. 



