ACRIDIUM 205 



cannot be seen until the ovary is removed, which should be 

 deferred until the ducts have been seen. 



Make a drawing showing the position of the parts of the 

 alimentary canal in side view. 



Cut the intestine and turn the alimentary canal poste- 

 riorly and anteriorly. 



5. Notice the muscles: 



(a) That move the abdominal segments. 



(b) That move the legs (those that supply the wings 

 have been destroyed). 



(c) That move the jaws. 



Do you understand now why the thorax needs to be 

 comparatively large and firm? 



6. The nervous system is directly comparable to that of 

 the lobster, but the connectives between the ganglia will be 

 found to be distinctly double and the ganglia to be somewhat 

 differently arranged. 1 



The ventral chain will be found to consist of a pair of 

 sub esophageal, three pairs of thoracic, and five pairs of ab- 

 dominal ganglia with the connectives between them. Which 

 of these are largest? Why is this the case? Trace the nerves 

 from them and see what organs they supply. 



Trace the connectives forward from the subesophageal gan- 

 glia and see that they pass around the esophagus, thus form- 

 ing the circumesophageal connectives. Cut away the dorsal 

 portion of the head and expose the cerebral ganglia. 



Add the nervous system to the figure that shows the alim- 

 entary canal. 



7. Trace the oviducts down around the sides of the body 

 and notice that they unite with each other ventral to the ner- 

 vous system, to form the vagina. This may be traced to its 

 opening between the plates of the ovipositor. Dorsal to the 

 vagina, opening to the exterior very near it, is a small sac, the 



x The arrangement of the ganglia in insects is very variable, show- 

 ing many gradations in concentration. 



