A HISTORY 
OF 
RECENT CRUSTACHA 
THE MALACOSTRACA 
CHAPTER I 
OUTLINE OF CLASSIFICATION 
Ir is conceivable that by origin all the animals of the globe 
belong to a single family. They now exhibit very great 
divergence. Between a star-fish and a crocodile, for ex- 
ample, the cousinship is obscure and remote. Yet almost 
all species may be included within a few principal clans, 
and these are united one to another by a small number of 
intermediate forms of life. For the whole series the de- 
tails of classification will vary with the increase of know- 
ledge. No system has yet been accepted as final. One, 
which is sufficiently good for our present purpose, dis- 
tributes animals among nine leading divisions. These are 
(1) the Protozoa, primitive animals, such as the Foramini- 
fera and Infusoria ; (2) the Coelenterata, in which the body- 
cavity serves alike for circulation and digestion, a tribe 
which includes sponges, corals, and jelly-fish; (8) the 
Kchinodermata or prickly-skinned animals, embracing the 
sea-lilies, star-fishes, sea-urchins, sea-cucumbers, and a 
