CHAPTEB XIV 



MARINE VERTEBRATES 



THE vertebrates form the highest sub -kingdom of animal life the 

 sub-kingdom to which we ourselves belong, the chief distinguishing 

 characteristic of the group being the presence of an internal 

 skeleton, the principal part of which consists of a rod or column 

 of cartilaginous or bony material running along the dorsal side 



of the body, known as the verte- 

 bral column. 



This column is usually com- 

 posed of a number of elements 

 called vertebrae, each of which 

 gives off two processes that unite 

 and form an arch on its dorsal 

 side, while all the arches form a 

 tube through which passes the 

 central portion of the nervous 

 system. 



Below, or on the ventral side 

 of the column, is the body-cavity 

 containing the organs of diges- 

 tion and circulation ; so that if 

 we make a transverse section of 

 a vertebrate animal we find that 

 there are two distinct tubes or 

 cavities a neural or cerebro- 



Fio. 225. TRANSVERSE 

 THROUGH THE BONT 

 WORK OF A TYPICAL 

 BBATE ANIMAL 



i 



SECTION 



FRAME- 

 VERTE- 



Spinons process of the vertebra. 2. 

 Neural arch. 3. Transverse process, 

 5. Body of the vertebra. 6. Breast- 

 bone. 7. Rib. The space between 2 

 and 5 is the neural cavity ; and that 

 between 5 and 6 la the visceral cavity 



spinal cavity on the dorsal side 



of the vertebral column, formed by extensions from the substance 

 of the latter, and enclosing the chief portion of the nervous sys- 

 tem ; and a body-cavity on the ventral side containing the viscera 

 or internal organs. 



The above features are highly important, and will always prove 



