in the Fish Gallery of the Indian Museum. 13 



in temperate regions. They are predaceous, attaching 

 themselves to their living prey— a fish — by their adhe- 

 sive mouth, in the manner of a parasite. 



The Hag-fishes are found in the seas of the colder 

 parts of temperate regions : they feed in much the same 

 way as the Lampreys, but often bore their way right 

 into the abdominal cavity of their living prey. 



FISHES. 

 [Cases 6-64.] 



The Fishes constitute one of the five main divisions, 

 or Classes, of the Craniate Vertebrates. 



The Vertebrata are defined, in the most general way, 

 as Coelomate § Metazoa t possessed of the three follow- 

 ing characters : — 



(1) A dorsal axial skeleton, which, in a few of the 

 lowest and in the earliest embryonic stages of the 

 higher Vertebrata, consists of a simple unsegmented 

 soft rod (notochord), but which in the great majority of 

 Vertebrata is gradually replaced, in the course of 

 development, by a firmly-jointed chain of bones (verte- 

 brae), known as the vertebral column, or backbone. 



(2) A central nervous system lying to the dorsal side 

 of the axial skeleton (notochord, backbone) in special 

 processes of which it is usually enclosed. This dorsal 

 nervous system is at first tubular. 



§ Metazoa are animals that consist of a multitude of reciprocally-interde- 

 pendent cells of various form function and arrangement : in contradistinc- 

 tion from Protozoa, or animals that consist either of one single independent 

 cell, or of a small mass of cells quite similar to one another in form and 

 function, and independent of one another. 



t Coelomate Metazoa are those that possess a body-cavity, or coelom, in 

 which the digestive tube is suspended and the viscera are lodged : in contra- 

 distinction from Coelenterate Metazoa, in which the only hollow of the body 

 is the digestive cavity. 



