18 INTRODUCTION TO ZOOLOGY. 



15. See the nerves branching off from the ganglia. 



16. In the head, between the compound eyes, find 

 the supra-oesophageal ganglion. Find the optic nerves 

 leading from this to the eyes. Trace the two parts of 

 the nerve cord from the supra-oesophageal ganglion 

 around the oesophagus to the infra-oesophageal gan- 

 glion below the oesophagus. 



17. Make a complete drawing of the nervous 

 system. 



18. "What drawings have you made? 



19. Copy the following words into your notebook ; 

 spell ; pronounce. Tell to what each term is applied. 



Questions to be Answered by Observing a Live Grass- 

 hopper. 



1. Watch the breathing. What movement is 

 visible in the abdomen? 



2. Observe a spiracle. Does it open and shut? 



3. In what order are the legs moved while walking? 



4. Why does the grasshopper spit out ' ' molasses ' ' ? 



5. Does the grasshopper have as good means of 

 breathing as man? Of locomotion? Of seeing? 



To the Teacher. 



The purpose of this study of the grasshopper is to train the pu- 

 pil to get knowledge at first hand and to get clear ideas of the object 

 studied, to give him practice in concrete analysis, and to train 

 him to use the mind in its power of abstraction. This purpose will 

 be defeated if he be told too much, if he be sent to books of reference, 

 or be allowed to find an answer to the questions proposed by asking 

 another person. It is not the knowledge gained that is of value, but 

 the power acquired in gaining the knowledge. If the knowledge be 

 acquired in the wrong way, there can be but little gain in power. 



