THE FROG l6l 



The neural arch is enlarged in the head to form the skull 

 for the brain while the haemal arch is enlarged below to 

 hold the vital organs. Animals with these characteristics 

 are called vertebrates. 



(2) The class Pisces, or fishes, occupies a median posi- 

 tion between the lowest and highest classes of this branch. 

 The principal subclasses are as follows:- 



(i). Selachians- — fishes with cartilaginous skeletons. Examples, 

 sharks and rays. 



(2). Ganoids — fishes with cartilaginous and bony skeletons, and 

 usually having ganoid scales. Example, garpikes. 



(3). Teliosts — fishes with skeletons composed altogether of 

 bony matter and having cycloid or ctenoid scales. Examples, all 

 common food fishes. 



(3) Read about the various food fishes, the manner 

 of catching, preparing, and using them. For what other 

 purpose are fishes used besides food ? 



Find out all you can about the fish industry. 



(4) In order that we may understand the position of 

 fishes in the branch vertebrates, the classes are given below : 



(i). Tunicates. 2. Lancelets. (3). Lampreys. (4). Fishes. 

 (S). Frogs. (6). Reptiles. (7). Birds. (8). Mammals. 



THE FROG. 



Rana sp. 



[Note. — If the living specimen cannot be obtained nearly all of 

 the following questions can be answered from an alcoholic speci- 

 men.] 



General Suggestions. — (i) The frog is the most com- 

 mon and best known form of the Amphibians. It is harm- 

 less and is always interesting to the observer. Specimens for 



STU. IN ZOOL. — II 



