366 ZOOLOGY 



OBSERVATIONS ON THE LIVING ANIMAL 



Each student, or set of students, should be provided with the 

 following: (1) a cage of wire netting about 8 inches cube, with a 

 door on top ; (2) a tin box or small cigar box, closed except for 

 a f-inch hole and small enough to be put into the cage. 



1. Enumerate the kinds of activities of the mouse in the cage. 



2. Bring a piece of toasted cheese to one side of cage. Note any 

 change of movements. 



3. Place the small box in the cage. Note the actions of the mouse. 

 Does he go directly to the hole or does he find it by accident, or 

 otherwise ? 



TOPICS FOR FURTHER STUDY 



1. The distribution of mice and rats. 2. The habits of rats and 

 mice. 3. The food of mice. 4. The races of tame mice. 5. Other 

 rodents. 6. Other mammals : the monotremes, marsupials, edentates, 

 Cetacea, Ungulata, Insectivora. Carnivora, Cheiroptera, and Primates. 

 7. The descent of man. 



XXI. DEVELOPMENT OF THE FROG'S EGG 



The eggs of toads and even of Urodela may be substituted, 

 although this outline accords closely with Anura only. Frog-spawn, 

 may be obtained in April in ponds and marshes as jelly-like masses 

 containing the eggs. Toad-spawn occurs as threads intertwining 

 with the grass at the margins of shallow pools. Eggs may be 

 obtained from animals in captivity by placing breeding males and 

 females in a large glass aquarium in the laboratory. The eggs should 

 be studied shortly after being laid and at various later periods. 



DRAWINGS 



(While it is desirable that these be ma fie from the living ef/r/s, they may 

 be made from eggs killed in /tot water at 80 C.) 



1. A bit of spawn with a few eggs in place, x 2. 



2. Isolate eggs, watch and draw various stages till hatching. The 

 series should include as many of the following stages as possible : 

 cleavage, inorula, blastopore formation, medullary folds, gill covers, 



