68 NATURAL HISTORY OF WASPS. 
assigned to them.* I can offer no opinion on this 
point, but, with others who scarcely can bring them- 
selves to think that such accurate observers can be 
really at variance, I would willingly believe that 
these differences m the description of the eyes of 
insects by different anatomists are founded in fact, 
not in error of observation. The description of the 
eyes in one insect—if it is not presumptuous to offer 
any suggestion—so correct in all its details, need 
not necessarily coincide with the microscopic linea- 
ments as carefully traced in another insect. Varied 
as the organs of insects are m every way, so exactly 
adapted in every particular to the wants of each of 
them, it is scarcely to be supposed that the eyes of 
them all would be identical in structure, and that the 
description of one would be applicable to the whole 
class. 
I have spoken of a more or less perfect form of 
structure. Let me qualify this expression, for it is 
one which there is often occasion to employ, and 
Entomology teems with illustrations of the fact, that 
what we might term defects are really, in relation to 
the whole animal, perfections. Perfect adaptation, 
‘not abstract perfection, is maintained throughout, 
A watch without any works at all is just as good for 
a child to wear as a chronometer. The perfect long- 
sighted eye of a bird, with all its wonderful adapta- 
tions, would be worse than useless, even had it ‘yet 
another adaptation to enable it to act in water, in 
the mantle of a scallop. <A little Crustacean, the 
whole thickness of whose microscopic body is per- 
meable by chemical diffusion, needs no mechanical 
* See ‘ Cyclopzedia of Anatomy and Physiology,’ Vol. II, p. 960. 
