ACRIDIUM. 169 



Cut the intestine and turn the alimentary canal posteriorly 

 and anteriorly. 



5. Notice the muscles: 



(a) That move the abdominal segments. 



(6) 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 compar- 

 atively 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 abdominal 

 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 sub-esophageal ganglia 

 and see that they pass around the esophagus, thus forming 

 the circum-esophageal connectives. Cut away the dorsal portion 

 of the head and expose the cerebral ganglia. 



Add the nervous system to the figure that shows the alimentary 

 canal. 



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

 and notice that they unite with each other ventral to the nervous 

 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 sperma- 

 theca, which serves to store the spermatozoa received from 

 the male until the eggs are laid. 



The reproductive organs may also be added to your figure show- 

 ing internal anatomy. 



Brooks: Hand-book of Invertebrate Zoology. 



1 The arrangement of the ganglia in insects is very variable, showing 

 many gradations in concentration. 



