Crabs, Lobsters, Shrimps, Wood-lice, Barnacles, etc, 671 



Photo by W. P. Dante, F.Z.S.] 



ACORN-BARNACLE. 



[Regent's Park. 



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

 difficult to believe the two 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 number 

 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 

 aberrant species the number is more variable. 

 In their early stages they 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 typical 

 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 with the 



crabs and lobsters, because, when they are young, 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 by the head, and develop a shell, usually composed 



of several pieces. The commonest is the ACORN-BARNACLE, the white shell of which, measuring 



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 country, 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 antennae, 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 decaying 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 



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



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



but others are 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 



Photo by W. P. Dando, F.Z.S. 

 Regent's Park. 



WOOD-LOUSE. 

 A land representative of a numerous 



marine group. 



