350 THE INVERTEBRATA 



as a preischium (pp. 298, 299). The exopodite is broad and there is a 

 very large epipodite, which serves as a gill. (The related Paranebalia, 

 however, has a slender exopodite with a fiagellum, and a small 

 epipodite.) The first four pairs of abdominal limbs are large and 

 biramous, the fifth and sixth small and uniramous. 



The alimentary canal possesses a proventriculus of relatively simple 

 type, several pairs of simple mid gut coeca, and an unpaired posterior 

 dorsal coecum. The heart is long, reaching from the head to the 4th 

 abdominal somite. The nervous system is of primitive type (p. 303). 

 The excretory organs have been alluded to on pp. 309, 311. 



Fig. 254. A female of Nebalia hipes. From Caiman, after Claus. a.' an- 

 temiule; a." antemia; ab.^ and ab.^ first and sixth abdominal limbs; add. ad- 

 ductor muscle of carapace; /. ramus of caudal furca; p. palp (endopodite) 

 of maxillule; r. rostrum; t. telson; i, 7, first and seventh abdominal somites. 



The animal /<?^^^ by straining particles from the water by means of 

 an elaborate arrangement of setae of different kinds on the thoracic 

 limbs, the necessary currents being set up by a pumping action of the 

 same limbs. These work upon a principle similar to that employed by 

 the Branchiopoda, the exopodites and epipodites acting as valves for 

 pumping chambers between the limbs, but it is the backward stroke 

 that enlarges the chambers, and they are closed by tho^ forward flap- 

 ping of their valves. Development is direct, the embryos being carried 

 by the long setae on the thoracic limbs of the mother. 



Subclass HOPLOCARIDA {STOMATOPODA) 



Malacostracawith a shallow carapace which is fused with three thoracic 

 somites and leaves four uncovered; two free pseudosomites on the 

 head; stalked eyes; the first five thoracic limbs subchelate and the 

 last three biramous; no oostegites; a large abdomen whose first 



