M i c r o s c o p i c a l E s s a y s .
The eyes are generally convex; they have no eye-brows, the
outer tunic is hard and tranfparent, having no external mo’tion
the genus o f canceri or crabs excepted. The eyes -of the greater
number appear, when examined by the microfcope, to be out
into a multitude o f little planes or facets, like the facets of a
diamond, having to the naked eye the appearance o f net-work
Each o f thefe fmall facets is fuppofed to poffefs the powers and
properties o f an eye. Leeuenhoek counted 3181 of-thefe facets
in the cornea o f a beetle, 8000 in thofe o f a fly. As the eyes of
infeQs are immoveable, they would have loft fight of many ob-
jeSs, if their eyes had been framed like thofe of other animals ;
but by means o f their multiplied eyes, they can eafily view fur-
•roundmg objefts-: nor is it at all improbable, that, .as objefts do
not appear double to our eyes, but that they are ftrengthened,
and many ifalfe appearances arc corrected by the ufe of both; fo
the numerous inlets to fight in -an isfoa may increale their field
o f view, augment the intenfity o f the light, and be productive o f
other advantages, -of which we can. form no conception. The
eyes o f infests differ in colour, feme being fcfrnd ©£ every
colour, and of inexpreffible beauty and foiighbaefe.- -■
The anterinas are -fine -and {lender horns, ■ corafiftijag o f
■ feveral articulations, moveable in various direCliorrs. They are.
beautiful in form, of a-delicate ftruQure, and are placed in the
fore part o f the h ead: they vary in different infeCls, «not -only in
fte ir fhape, 'their length, their bulk, but affd in-the number -of
their articulations. The -antenna; o f the male -infeSt generally
differ from thofe o f the female: they form one o f the moft dif-
tinguifhing charafleiifiics o f infefts, and one of the means of
judging ‘to 'what -genus they belong. The gtfeateft number of
® .iiafeCls
M i c r o s c o p i c a l E ss a v s . 175
infeCls have only two antennas; the onifeus, the pagurus, and
aftacus have four ; indeed Fabliaus gives fix to the latter.* O f
the ufe they are to thefe little animals, or the end of the Creator
in forming them, we are altogether ignorant: fome writers have
conjectured that they were the organs o f fmell and hearing; others
have fuppofed that they were appropriated to a feeling more
delicate than our own, and fenfible to the leaft motion or dif-
turbance in the ambient fluid in which they move: feveral infects
cover their eyes with them when they take their reft. They
are characterized by naturalifts under the following names:
Setaceous' are.thofe that, like a brittle; grow gradually taper
towards their point or extremity.
F iliform, thread fhaped, and o f an uniform thicknefs.
Monilifo-rm ; thefe’are o f a regular thicknefs, but confift o f
a feries of knobs, like a necklace of beads.
C l a v a t e d , formed like a club, increafing gradually from the
bafe to the extremity.
C a p it a t e d ; thefe'are alfo formed like a elub, but the laft
articulation is larger than the reft, finilhing with a kind o f capital
or head.
F issiles ; thefe are like the former, only that the head is divided
into different parts or Iaminse.
Perfol i a te;
Fabricius Philofopfiia Entomologica, p. ig.
■ ■ HBjjjll