CRUSTACEA. 31 



72. Beside the tentacula, the cuttle-fish is furnished with 

 a pair of arms, with the ends expanded, .and also fur- 

 nished with suckers. These long members are employ- 

 ed as cables, and the suckers as anchors, by which these 

 animals fix themselves firmly to/ rocks during violent 

 agitations of the sea, and without which they would un- 

 doubtedly sometimes be dashed to death against the 

 rocky shores. These long arms are not employed by 

 the animal in swimming, the short ones being used as 

 oars for the purpose of impelling this singular creature, 

 not forward but backward, for in this manner do all the 

 cuttle-fish tribe swim. Some of them are fifteen or 

 twenty feet long. 



ARTICULATA. 



73. The animals now to be noticed are articulated, or 

 are provided with joints, by means of which their hard and 

 inflexible parts become the instruments of motion. 

 Hence this division includes animals having joints, wheth- 

 er large or small, and by which they are at once distin- 

 guished from the mollusca, where nothing analogous to 

 articulation exists. This division contains a vast assem- 

 blage of living beings, including the insects, fishes, and 

 quadrupeds. The limits of this work will, however, 

 allow*an account of the physiology "of only a few of the 

 most curious and important. 



CRUSTACEA. 



74. The Crustacea are animals encased in a compact, 

 crusty frame work, composed chiefly of carbonate of lime, 

 as the lobster and crab. 



75. The joints of crust aceous animals are constructed in 

 the most admirable manner, by which in most cases 

 every part of the limb can be moved in all directions 

 They have either three or four pairs of legs, each of 

 which is divided into five pieces, by as many joints. On 

 each side of the head there are long, and often very 



Why are certain animals denominated articulata? What races of 

 inimals are articulated ? What are the Crustacea ? What parts of 

 ;hese animals are called antennae ? 



