BOOK V. JOINTED ANIMALS.
CHAPTER I.
THE CRAB AND SCORPION GROUPS.
BY W. F. KIRBY, F.L.S.
This section of animals is often called a "sub-kingdom," and differs from back-boned animals in having the framework of the body outside. That is, instead of a skeleton, Crabs, Spiders, Centipedes, and Insects are protected either by a hard shelly casing, or by a tough skin, to which the muscles are attached; and this arrangement renders them much stronger and much less susceptible to injury, in proportion to their size, than vertebrate animals. They have cold blood, generally of a white colour; and their bodies and limbs are usually composed of a considerable number of separate joints.
Photo by E. Connold.
BARNACLES.
A species which commonly attaches itself to ships' bottoms and floating wreckage.