510 THE OCEAN WORLD. 
shell; but M. Liesk has often seen the operation. The crab begins 
by tearing off the fibre at the extremity where the fruit is, always 
choosing the right hand. When this is removed, it strikes it with its 
great claws until it has made an opening; then, by the aid of its 
slender claws, and by turning itself round, it extracts the whole 
substance of the nut. 
The Crustaceans have eyes of two kinds, simple and compound : 
the first are séssile and immovable, and very convex ; the others 
are borne on short calcareous stems or peduncles, and are formed of 
a number of small eyes symmetrically agglomerated together—the 
reunion of all the microscopic cornea of a composite eye—resembling 
in shape a cap formed of facets. It is said, for instance, that the eye 
of the lobster consists of 2,500 of these little facets. The simple 
eyes are short-sighted—the compound eyes are for more distant and 
perfect sight. They appear to have a strong sense of smell. Many 
of them cannot swim, but walk with more or less facility at the 
bottom of the water. It is said, for instance, that the cavalier of the 
Syrian coast, Oxypoda cursor (Fabricius), is named from the rapidity 
with which it traverses great distances. 
The class Crustacea may be divided into seven orders :—1. The 
Decapoda; 2. the Amphipoda; 3. the Lsopoda; 4. the Xiphosura ,; 
5. the Branchiopoda,; 6. the Entomostraca; and 7. the Cirripedia. 
The first of these orders is divided into three sub-orders :—Macrura, 
containing the Lobsters, Shrimps, and other long-tailed decapod 
Crustacea; Anomoura, containing the Hermit or Soldier-crabs ; and 
the Brachyura or short-tailed crabs, such as the common edible crab. 
The second order contains the common Sand-hopper ( Zaditrus locusta.) 
Among the families of the third order we may mention that of the 
Oniscide, to which the very common Wood-louse belongs. The 
fourth order contains but a single genus, Limulus. One of the 
most remarkable species of this genus is the Z. Moluccanus, the 
Molucca crab. It is distinguished by a long serrated spine or telson, 
which looks most formidable. They are in great request in the 
markets of Java. Linnzeus thought that the fossil trilobites were 
closely allied to the Zému/us. Latreille, on the contrary, classed 
them near Chiton, a genus of Mollusca. The body of Limulus so 
strikingly resembles that of many Trilobites, that the most common 
observers may perceive an affinity. The fifth order contains some 
very remarkable forms. We may specialise the genera Apus, Daphnia, 
and Cygris; and here also very probably belongs that family of 
extinct forms the Trilobites. The sixth order contains some non- 
parasitic forms, as Cyclops; it embraces a very large number of forms 
