160 
COMPENSATION. 
placed on each side of it, which lifts and depresses it a* 
pleasure.* 
V. The spider's web is a compensating contrivance 
The spider lives upon flies, without wings to pursue them; 
a case, one would have thought, of great difficulty, yet 
provided for; and provided for by a resource, which no 
stratagem, no effort of the animal, could have produced, 
had not both its external and internal structure been speci¬ 
fically adapted to the operation. 
VI. In many species of insects, the eye is fixed; and 
consequently without the power of turning the pupil to the 
object. This great defect is, however, perfectly compensat¬ 
ed; and by a mechanism which we should not suspect. 
The eye is a multiplying glass, with a lens looking in 
every direction and catching every object. By which 
means, although the orb of the eye be stationary, the field 
of vision is as ample as that of other animals, and is 
commanded on every side. [PI. XXX. fig. 8.] When 
this lattice-work was first observed, the multiplicity and 
minuteness of the surfaces must have added to the surprise 
of the discovery. Adams tells us, that fourteen hundred 
of these reticulations have been counted in the two eyes of 
a drone bee. 
In other cases the compensation is effected by the num¬ 
ber and position of the eyes themselves. [PI. XXX. fig. 9.] 
The spider has eight eyes, mounted upon different parts o^ 
the head; two in front, two in the top of the head, two on 
each side. These eyes are without motion; but, by their 
situation, suited to comprehend every view which the wants 
or safety of the animal may render it necessary for it to take. 
VII. The Memoirs for the Natural History of Animals, 
published by the French Academy, A. D. 1687, furnish us 
with some curious particulars in the eye of a chameleon. 
[PI. XXXI. fig. 1.] Instead of two eyelids, it is covered 
by an eyelid with a hole in it. This singular structure ap¬ 
pears to be compensatory , and to answer to some other sin¬ 
gularities in the shape of the animal. The neck of the 
chameleon is inflexible. To make up for this, the eye is 
so prominent, as that more than half the ball stands out of 
the head. By means of which extraordinary projection, 
the pupil of the eye can be carried by the muscles in every 
direction, and is capable of being pointed towards every 
object. But then, so unusual an exposure of the globe of 
the eye requires, for its lubricity and defence, a more than 
* Goldsmith’s Nat. Hist. vol. v. p. 274. 
