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 
num^ber; of a simple structure, and placed at a 
considerable distance from each other. 
Brit 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 Linnasus 
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 mi' 
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 
large Caterpillar, the anatomy of which has been 
given with laborious accuracy by Tyonett, the 
humber 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-^ 
