THE FROG. 



RANA SP. 



FROGS may be had at various times of the year, and are 

 easily kept in proper aquaria, so arranged that the animals 

 have range from water to dry or rocky support, provided 

 care is taken to guard against serious contamination of tank 

 or water. They may be secured in late summer or fall, or 

 even in spring, though in New York State there is now a 

 closed season in the spring as for other game animals. In 

 addition to living specimens kept during the year there 

 should also be an ample supply of preserved material for 

 the needs of classes. If specimens are to be injected for 

 study of the blood system this must be done immediately 

 after killing preparatory to preservation. 



In the neighborhood of larger cities frogs may often be 

 secured through fish markets, provided attention is given 

 to the subject in ample time, and often at prices much lower 

 than those charged by professional supply departments. 



I. External Characters. 



What is the shape of the body as a whole? Are dorsal 

 and ventral surfaces well marked? How? Note the di- 

 vision of the animal into head, trunk, and limbs. Is there 

 a neck and tail? What is the character of the skin? In 

 the living animal is the skin moist or dry, warm or cold? 

 Are there scales or other protective structures in the skin? 



1. Head. Note its triangular shape. Observe the follow- 

 ing parts : mouth, nostrils, eyes, ear-drum or tympanic mem- 



