THE FUNCTION AND STRUCTURE OF FINS 449 



below — the ventral fin ; and one at the end — the tail fin. The 

 function of the last has been already considered. The generally 

 accepted ideas on the functions of the others are well expressed 



8 



i 



12 



13 



14- 



IS 



in the following quotation : " To give stability to the body, 

 and to steady its course when swimming, the fish has a dorsal 

 and ventral keel, formed by the anal and dorsal fins, which 

 like the sliding keel of a 3'acht can be raised or lowered as 

 occasion requires. When these fins are removed the course 



