COPEPODA. BRANCniURA. 



437 



The Branchiura are often placed near the Caligidce, but they differ 

 from them and from the true Copepoda in several essential particulars. 

 In the general body form they certainly resemble the Caligidce 

 except in the hind part of the body, which is split into two plates 

 (caudal fins). Their internal structure, however, and the structure 

 of the appendages distinguish them from the above-mentioned 

 parasitic Crustacea. A large suctorial tube projects above the mouth, 

 and in it are concealed finely serrated mandibles and styliforrn 

 maxilla?. A little above this proboscis there is inserted a long 

 cylindrical tube, which terminates in a retractile styliforrn spine, and 



contains 

 pair of 



the 



glandular 



A' 



ducts of a 

 tubes 



said to be poison glands. 

 Powerful organs of attach- 

 ment are placed on each 

 side of and beneath the 

 mouth ; they consist of 

 two parts (1) of an an- 

 terior pair of appendages 

 which correspond to the 

 anterior maxillipeds and 

 are in Aryulus modified 

 into large sucking discs, the 

 hook-bearing terminal por- 

 tion being reduced ; and (2) 

 of a posterior pair, which 

 corresponds to the second 

 pair of maxillipeds, and is 

 provided with numerous 

 spines on its broad basal 

 portion, a tactile protube- 

 rance and two curved termi- 

 nal claws at its extremity. 

 Next to these come the four paired swimming feet of the thoracic re- 

 gion, which, with the exception of the last, are, as a rule, covered by the 

 sides of the cephalo-thoracic shield. Each of these consists of a large 

 many-jointed basal portion, and two much narrower ranii, which are 

 beset with long swimming setse and in their form and setigerous 

 investment are not unlike the biramous appendages of the Cirripedia, 

 being like them derived from the Copepod-like feet of the larva 

 (fig. 347). 



FIG. 317. Young male of ArytJus foliaccvt. A', 

 Anterior antennae ; Sg, sucker (anterior maxilli- 

 ped) ; Kf", maxilliped ; Sf, swimming feet, 

 21, rostrum ; St, spine ; D, intestine ; T, tcstes. 



