LECTURE IX. 91 



Call a magnifying meniscus, having the outward 

 or convex part of a smaller sphere than the con- 

 cave or interior. 



In Spiders the eyes are from six to eight in 

 number; of a simple structure, and placed at a 

 considerable distance from each other. 



But besides the eyes just described, or those 

 placed on each side the head, there are on the 

 heads of many insects two or three small separate 

 eyes, of a simple structure, and seated on the top 

 of the head. They have been called by Linnaeus 

 by the title of Stemmata, and their real nature is 

 not clearly understood. 



The Muscles, or organs constituting the several 

 portions of the flesh in insects, are far more nu- 

 merous than in the larger animals, and are ex- 

 tremely sensible or irritable. In the human body 

 it is observed, that the muscles can hardly be said 

 to exceed the number of five hundred ; but in a 

 krge Caterpillar, the anatomy of which has been 

 given with laborious accuracy by Lyonett, the 

 number of the muscles amounts to more than four 

 thousand. 



The comparative powers of the muscles in in* 

 sects are also far stronger than in the larger ani- 



