5IO 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 sessile 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 : i. The 

 Decapoda; 2. the Amphipoda; 3. the Isopoda; 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 (Tatitrus locusta.) 

 Among the families of the third order we may mention that of the 

 Onisridce, 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 L. 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. Linnaeus thought that the fossil trilobites were 

 closely allied to the Limulus. 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 t 

 and Cypris ; 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 



