86 ZOOLOGY. 
‘The organs called antenne are jointed filaments with which the 
head is furnished, one on each side, and are evidently very delicate 
organs of touch. The creatures which possess them seem to feel their 
way by them, and to them is ascribed the bee’s power of working in 
the dark. Some suppose that they are also organs of hearing, and by 
means of them it would appear that some insects, as bees and ants, have 
the power of communicating with each other. They possess great flexi- 
bility, but differ much in the number of joints of which they are composed, 
and also in their form, some being threadlike, some club-shaped, some 
feathered, &c. in endless variety. 
Crustacea.—The remaining classes of Articulata—namely, Orustacea, 
Arachnida, and Insecta—all have the body generally less elongated than 
the Annelide and Myriapoda, the division into segments quite distinct, and 
the circulating and nervous systems much concentrated in those segments 
with which the organs of special sense and of locomotion are connected. 
All of them have articulated limbs, and Insects are also very generally 
furnished with wings, which neither Crustaceans nor Arachnids possess. 
The Crustacea derive their name from their external skeleton, the hard 
armour which in most of them covers the whole body, and which, in those 
of highest organisation, is very complex in its structure. The body in 
Crustaceans, as in Arachnids and Insects, consists of three segments, the 
head, thorax, and abdomen. In Crustaceans and Arachnids, the head and 
thorax are very much combined into one piece, whilst in Insects they are 
perfectly distinct. All the organs of special sense are connected with the 
head, and the limbs with the thorax; but in many Crustaceans, as the 
lobster, prawn, and shrimp, the principal organ of locomotion is the 
abdomen, which terminates in fan-like appendages. By bending the 
abdomen suddenly down under the thorax, they dart backyard in 
the water. The limbs of some are aaer for swimming ; those of 
others are used for walking at the bottom of the water or on dry 
ground, The first pair of legs is not unfrequently transformed 
into powerful claws or pincers, as in crabs and lobsters. The limbs 
of the first thoracic rings are, in many Crustaceans, organs not of 
locomotion, but meee with the mouth, and eae for tearing 
food. The respiratory organs of all the Crustaceans are adapted to 
an aquatic life; even those which live on land being generally inhab- 
itants of damp places and breathing by means of gills. Crustaceans 
are all oviparous ; ; and they undergo remarkable metamorphoses 
after issuing from the eg, before they attain their adult form, after 
which, however, they still increase in size, moulting or casting the shell 
foenente 
The minute Crustaceans, which abound in lakes, cae and rivers, as 
well as in the sea, are of great use in the economy of nature, consuming 
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