THE GRASSHOPPER 119 



of the digestive tube ending at the anus. The intestine is 

 made up of three parts. 



3. Excretory System. This comprises a number of deli- 

 cate capillary tubes, the Malpighian tubules, which are 

 twisted together and may partly fill the body cavity. They 

 connect with the digestive canal at the point where the 

 stomach and intestine join. 



4. Reproductive System. The reproductive organs, testes 

 or ovaries, are present in the abdomen, dorsal to the digestive 

 tube. These organs are made up of tubules closely packed 

 together. They open to the exterior through the sperm 

 ducts or oviducts, whose openings are ventral to the anal 

 opening. The ovary in mature animals may be a mass of 

 eggs completely filling the body cavity. 



Make a large drawing to show all the organs and systems 

 worked out. 



5. Nervous System. Remove the alimentary canal and 

 the reproductive organs. The nerve cord should now appear 

 along the median ventral line, covered over with a thin 

 sheet of fat tissue. Are ganglia present? How many 

 in the abdomen? In the thorax? Is there a ganglion to 

 each somite? Where are the ganglia largest? Trace the 

 general direction of the nerves which leave the ganglia. 

 In the head is a ventral inf ra-esophageal ganglion, and a dorsal 

 supra-esophageal ganglion or brain. These two large ganglia 

 are connected by circum-esophageal commissures. From the 

 brain nerves go to the ocelli, compound eyes, and antennae. 



Make a large drawing showing the nervous system. 



Compare the crayfish, the grasshopper and the earth- 

 worm in regard to: (a) The plan upon which the body is 

 constructed; (6) the organization of somites into well 

 defined regions; (c) the arrangement and structure of the 

 appendages; (d) the number, position and structure of 



