360 



ARTHROPODA 



capillaries, and veins are well developed, but with the diffuse respiration 

 only the heart persists as a reduced structure, or with its disappearance 

 the last traces of a circulatory system are lost. 



Locomotion is also related to the aquatic life and these animals usually 

 possess appendages of the biramous or schizopodal type, which at once 



FIG. 374. Copepod appendages. I IV, Diaptomus castor; I, a pair of schizopodal 

 feet; II, second right antenna: 777, right mandible; IV, right maxilla; V, right mandible 

 of Cyclops coronatus. i, 2, joints of basiopodite; /, endopodite; a, exopodite. 



differentiates these forms from all other arthropods. While in the latter, 

 as every insect shows, the joints of the limb are in a single row, the crus- 

 tacean appendage has a two-jointed base (basiopodite}, followed by two 

 many-jointed branches (fig. 374, 7), an fnner or endopodite and an 

 outer or exopodite. 



FIG. 375-- 



-7 and 77 first and sixth legs of Bronchi pus grubei (after Gerstacker). 

 a, flabellum; b, basis; /, axon and its endites; k, gills. 



The schizopodal appendage occurs only when the limb is used for swimming; 

 when it is used for walking, as in crayfish and crabs, the exopodite is lost and 

 only the endopodite persists as the functional limb, which then closely resembles 

 the appendages in the insects. This loss rarely occurs on all the appendages; 



