LOBSTEE OR CRAYFISH 161 



1. The cardiac ossicle, extending across roof of 



cardiac cavity. 



2. The pyloric ossicle, extending across roof of 



pyloric cavity. 



3. The lateral cardiac ossicles, attached to ends 



of 1. 



4. The lateral pyloric ossicles, attached to ends 



of 2. 

 6. The uro-caMiac ossicle, passing backward 

 from 1. 



6. The prepyloric ossicle, passing backward and 



downward from 2. 



7. The gastroUth, in the anterior cardiac wall. If 



this is not found, see if there is not a thicken- 

 ing of the cuticle in this region. 



Divide the stomach accurately along the 

 middle line with a pair of scissors, and look for 



8. The postero-ventral ossicles, in the posterior 



wall of the cardiac sac. Do you find any other 

 ossicles than those mentioned ? 

 Make a drawing of the framework formed by the 

 ossicles. 



Look also for 

 I. The gastric teeth. 



1. The median tooth (lying between the ends of 



the two median ossicles). — What is its shape ? 

 Size ? Color ? Does its tip touch against any 

 other part ? 



2. The lateral teeth (attached to the lateral py- 



loric ossicles). — Compare with 1. 



Gently pull upon the cardiac and pyloric 

 ossicles in such a way as to imitate the action 

 of the muscles attached to these parts. What 

 motion do the teeth make ? 



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