in the Fish Gallery of the Indian Museum. 1 7 



The Topography of the Body of a typical fish may- 

 be studied from the lettered preparation of a Sea-perch 

 (Lates calcarifer : Bekti) in Case 8. 



The head is delimited from the trunk by the gill- 

 opening, the slit by which the water that has been used 

 in breathing ultimately escapes from the pharynx. In 

 the head we see (1) a wide mouth, (2) eyes without true 

 eyelids, and (3) nostrils, which do not, however, open 

 into the pharynx. There are no external signs of an 

 ear, because the organ of hearing in fishes is lodged 

 within the bones of the head. 



The trunk is delimited from the tail by the vent : the 

 tail is the tapering part behind the vent. 



In the middle line of the back is a fold of skin sup- 

 ported by rays : this is the dorsal fin, which may either 

 be entire or be cut into two or three pieces. In the 

 middle line of the under surface of the tail, occupying 

 part or all of the space behind the vent is a similar fold 

 of skin supported by rays : this is the anal fin. Extend- 

 ing vertically round the tail is a third similar fold of 

 skin supported by rays : this is the caudal fin, which is 

 very often forked. These three series of fins are known 

 as the vertical or unpaired fins: the manner in which 

 their rays are loosely articulated with the skeleton may 

 be studied in the labelled skeleton of the Cod-fish in 

 Case 9. 



Besides these vertical unpaired fins, there are, in the 

 specimen we are examining, on the trunk, two symmet- 

 rically paired fins. The front pair, placed immediately 

 behind the gill-opening on either side, are the pectoral 

 fins : they correspond with the fore-limbs of higher 

 Vertebrates. The hind pair, which stand out on either 

 side of the belly behind the level of the pectorals, are 

 the ventral fins : they correspond with the hind limbs 

 of higher Vertebrates. 

 3 



