ANATOMY AND PHYSIOLOGY. 67 
On abstract optical principles it is inferred that 
these two kinds of eyes have different properties. . 
The single eyes, constructed like those of fishes, are 
intended, like those, for near vision. The compound 
eyes take in distant objects and a wider field; dis- 
tinctness being secured by the spaces into which the 
picture is divided; and the extent of the field being 
in direct proportion to the extent of the surface of 
the cornea and to the degree of its convexity. An 
experiment shows so very little, that one would 
rather trust to general observation and to the ana- 
tomical examination of an organ, than to any con- 
clusions from experiments, as to its functions. How- 
ever, experiments have not been wanting* on the 
question of the nature and functions of the parts 
which we call eyes. And by coating them with 
black varnish the same conclusions were reached 
which have been more surely attained by inference 
from their structure and optical arrangements. 
The eyelashes of the honey-bee, just alluded to, 
are supposed to add to the distinctness of vision by 
separating the different parts of the mosaic pattern 
which is impressed on the retina, and thus localizing 
more exactly the objects in the field of view. 
Such are the descriptions of Miiller, and the con- 
clusions which he has drawn from them. They are 
not, however, universally accepted in all their details. 
For some anatomists suppose that the structure of 
the units of the compound eyes is more elaborate, 
and that they have a higher function than Miiller has 
_ * See a notice of these experiments in Van der Hoeven’s ‘ Hand- 
book of Zoology, translated by Dr. Clark,’ Vol. I, p. 280. 
FQ 
