AMPHIPODA 



359 



and maxillipeds are shown in Fig. 265. The maxilUpeds latter pair 

 are united by the fusion of their coxopodites. The first two pairs 

 of legs are subchelate, the third and fourth pairs are turned forwards 

 and help the subchelae in feeding, the last three pairs are turned 

 backwards and used when the animal crawls on its side. The first 

 three pairs of abdominal limbs are used in swimming and to direct 

 water towards the gills, the last three pairs are used together to kick 

 the ground in jumping. Simple gills (epipodites) are found on the 

 coxopodites of the legs, and oostegites on those of the third to fifth 

 pairs in the female (Fig. 266). The alimentary canal has a single- 



\'Th.l 



pxa. 



Th,8 



Fig. 264. Gammarus neglectus. Female bearing eggs seen in profile. From 

 Leuckart and Nitsche, after G. O, Sars. cpx. cephalothorax ; Th. free thoracic 

 somites; ah. the six abdominal somites; an.' antennule; an." antenna; 

 md. mandible; mx.' maxillule; mx." maxilla; mxpd. maxilliped; Th.z- 

 Th.S, thoracic limbs; ab.i-ab.^, three anterior abdominal limbs for 

 swimming; ab.4^-ah.6, three posterior abdominal limbs for jumping; h. heart 

 with six pairs of ostia; ov. ovary; hep. hepatic caecum; p.ca. posterior caeca 

 of the alimentary canal ; med.d.cm. median dorsal caecum ; at. alimentary 

 canal; n.sy. nervous system; o. ova in egg pouch, formed from oostegites on 

 the coxae of the second, third and fourth thoracic limbs. 



chambered but complex proventri cuius, two pairs of '' hepatic " coeca, 

 and a pair of coeca at the hinder end of the mid gut which have 

 been supposed to be excretory. The principal organs of excretion are 

 antennal glands. The heart extends from the 7th to the ist thoracic 

 somite. The young are born with all their legs. The females with 

 young are carried by males and eventually re-impregnated. 



