PARTS OF INSECTS, AND MISCELLANEOUS OBJECTS. 

 Fig. 231. 



137 



Fig. 230. 



ous irregular circles. The second tunic is a tissue more delicate and transparent, 

 and the third is formed of a cartilaginous thread, wound spirally upon itself. In 

 figure 236, are exhibited portions of the respiratory tubes of the silk-worm, con- 

 siderably magnified. The fibrous structure is at once perceived, and the end 



