VEETEBEATA. 77 



(c) the anal fin, the median fin on the ventral side 



just anterior to the tail ; 

 (cZ) the pectoral fins, the more anterior of the paired 



fins; 

 (e) the pelvic fins, the more posterior of the paired 

 fins. 

 7. Structure of the fins. 



a. Each fin is simply a fold of skin supported by- 

 numerous bony or cartilaginous rays. Identify 

 the rays in each fin. 

 What advantage is there to the fish in having the 



fin constructed in this manner ? 

 Why does the dorsal fin have hard bony rays 

 while the caudal fin has soft cartilaginous ones ? 

 h. Can the fins be closed ? 



If so, is any advantage gained thereby ? 



C. Sense Organs. 



1. Do you think there is any definite purpose in the 



movements of the fish ? (Give your reasons.) 



2. Identify the following Sense Organs, — 



(a) the nostrils, small openings in front of the eyes ; 



(J) the eyes ; 



(c) the " lateral line " indicating the position of 

 sense organs supposed to help the fish in bal- 

 ancing itself. 



3. The Nostrils. 



a. How many are there ? 



b. Do they open into the mouth ? (Dem.) 



c. Are they used in breathing ? 



d. Can a fish smell ? (Dem.) Give evidence. 



4. The Eyes. 



a. Why are they located on the sides of the head ? 



