60 INVERTEBRATE ANIMALS. 



Province ARTHROPODA. 



apSpov, a joint ; ttovj, a foot. 



Animals with jointed limbs articulated to the body. 



This great Province i^astly outnumbers in species the total of. the 

 preceding invertebrate Provinces, and exceeds them in the inte- 

 rest of its annals. The gathering up of several body -segments, 

 somites, to form a true head, here first appears, and with it appa- 

 rently a capacity for the higher orders of instinct. Prefigured in 

 Vermes, this arrangement attains perfection by multitudinous steps 

 and very slow degrees. The term Arthropoda is retained as a 

 convenient designation, but is inferior to Annulosa in expressing 

 the chief character of the present Sub-kingdom. 



Class CRUSTACEA, cntsto, a crust. 



Respiration generally by gills. Antennae, two pairs. 

 Jointed appendages, more than eight. The body of a 

 typical Crustacean is made up of about twenty-one seg- 

 ments or somites, often nearly equally distributed 

 between the head, the thorax, and the abdomen. 



The general arrangement of the Class is in accordance with the '' Histoire 

 Naturelle des Crustaces," par M. Milne Edwards; but advantage 

 has frequently been taken of the great work on the same subject by 

 James Dana, of the United States Exploring Expedition : this work 

 is a monograph of surpassing excellence. 



Sub-class CIRRIPEDIA. cirrus, a curl ; pes, a foot. 



In the larval state the Cirripedes are free and loco- 

 motive : subsequently two of the larval antennae discharge 

 a kind of glue, by which the head of the animal becomes 

 permanently attached to some solid object. 



Group 159. — Family BALANID^E and allies. /SaAavo?, an 

 acorn. In the family of Sessile-cirripedes, or Acorn- 

 shells, the head of the animal is fixed to the centre of a 

 shelly plate, the basis of a conical shell made up of 



