66 ELEMENTARY ZOOLOGY. 



Reproductive system. This differs, of course, in the male 

 and the female. The female has a pair of ovaries filling a 

 large part of the posterior segments of the abdomen. These 

 produce the eggs, which reach the exterior by way of tubes 

 known as oviducts. The testes, or spermaries of the male 

 correspond to the ovaries and produce the sperm or male 

 cells. These escape to the outside by delicate ducts. Eggs 

 are fertilized while still in the body of the female, and 

 receive afterward certain protecting and cementing materials 

 from the walls of the female tubes. 



Nervous system. This is ventral and runs the length of the 

 body. It is made up of a series of ganglia or nerve centres, 

 connected in a chain by nerve fibres. This chain is made 

 up of three regions: (i) a ganglion above the gullet which 

 is called the brain; (2) a loop of nerve fibres about the gullet 

 connecting the brain with, (3) a chain of ganglia scattered 

 along the length of the floor of the thorax and abdomen. 

 What is probably the special function of each of these 

 regions? 



The Crayfish (any Species). 



The questions asked for the grasshopper, with such 

 changes as would be suggested by the common sense of 

 teacher and pupil, will serve as a general guide for the 

 study of the crayfish. The mode of life is very different, 

 but the same general problems of life are to be solved by 

 both animals. 



75- Suggestions for field and laboratory studies. 



i. The general conditions of life. To what extent 

 does it use land? to what extent water? Is it heavier or 

 lighter than water? How is it affected by drouth and 

 by heat and cold? What is its food? What are its 

 enemies? How does it protect itself or avoid or escape 

 them? Has it any devices of concealment? How does 

 it behave when disturbed? When stones are turned 

 over? How does it behave when you try to grip it? 

 Is there any point where you can safely hold it? 



