CRABS, LOBSTERS, SHRIMPS, WOOD-LICE, BARNACLES 671 



Ph.io by (/'. P. Da„do, F.Z..9.] 



ACORN-BARNACLE 



iRfgtiil's Pari 



The general appearance is so different from the Stalked Barnacle that it 

 is difficult to belie-t'e the tzuo belong to the same group 



They are nearly all aquatic animals, by far 

 the larger portion being marine, and they 

 breathe with gills. They are provided with 

 a hard calcareous or horny covering. The 

 head is not separated from the trunk, as in 

 insects ; and they are provided with a num- 

 ber of jointed organs, usually classified as 

 three pairs of jaws, three pairs of foot-jaws, 

 and five pairs of legs in the more typical 

 families; but in the smaller and more aber- 

 rant species the number is more variable. 

 In their early stages the}' frequently pass 

 through very extraordinary changes of form, 

 but after assuming their adult shape they 

 grow by casting their shells at intervals. 



We will now notice a few t)'pical 

 examples of the different groups of these 

 creatures. 



The Brine-shrimp is a little reddish 

 creature about half an inch long, which 

 prefers the concentrated solution of brine-pits to sea-water. It has eleven pairs of legs, and, 

 notwithstanding its name, the front portion of its body is considerably broader and flatter in 

 proportion than that of a real shrimp, the other half consisting of a jointed tail. 



Barnacles were formerly considered to be shell-fish, but are now usually classed \\'ith the 

 crabs and lobsters, because, \\hen they are j'oung, they appear as freely swimming creatures, 

 with one eye, two antennas, and six pairs of jointed limbs. When they grow larger, they fix 

 themselves to a rock or some other object b)^ the head, and develop a shell, usually composed 

 of several pieces. The commonest is the Acorn-BARNACLE, the white shell of which, measur- 

 ing rather less than an inch across, swarms on rocks at the seaside. It is shaped like a limpet, 

 but open at the top. The GooSE-BARNACLES hang down by a stalk, and their jointed shells 

 more resemble those of a mussel than that of a limpet, though they are composed of several 

 pieces. Various species similar to both those mentioned are found on piers, rocks, the bottoms 

 of ships, and even sometimes on the skin of whales. 



In dark cellars in the countr)-, under loose bark, or under pieces of wood which have been 



left in the fields, we often see creeping about brown creatures 

 about half an inch long, with jointed bodies and antenna;, and 

 short jointed legs. They are called WOOD-LICE, and several 

 species roll themselves up into a ball when alarmed. These 

 creatures feed chiefly on deca}'ing vegetable substances; and 

 there is a larger marine species much like them, which is common 

 in holes and crannies in the rocks on the seashore. 



There are other curious creatures, called Whale-LICE and 

 Flsh-LICE, which are parasitic in their habits. Some of these 

 look like spiders, and one or two have enormously long legs ; 

 but others arc of strange and almost indescribable forms, and 

 sometimes without legs at all. One species, found on the sprat, 

 has two long appendages at the end of its body not unlike a 

 pair of compasses. 



Shrimps and Prawns are red when cooked, but when alive 

 are very pretty semi-transparent objects, which may be seen 

 swimming about through the glass of aquariums placed against 

 the wall. Prawns are larger than shrimps, and have a strong 



PhM I) U\ P. Dandt, F.Z.S. 

 Reg'-nt's Pari 



WOOD-LOUSE 



^ land reprcsentati-ve of a numerous 



marine group 



