PERACARIDA 



401 



antennae are much like those oi Ligia. The mandibles have the same 

 parts as those of Ligia ^ with a palp. The maxillules, maxillae, and 

 maxillipeds are shown in Fig. 279. The maxillipeds 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 



med.dxm 

 cpx, 



^{' Th. 



j^^^^:^^=^^> 



\-T/u7 



p.ca. 



Fig. 278. Gammariis neglectus. Female bearing eggs seen in profile. From 

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

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

 md. mandible; mx.' maxillule; mx." maxilla; ?nxpd. maxilliped; Th.2~ 

 Th.8, thoracic limbs; ab.i-ab.2, three anterior abdominal limbs for swim- 

 ming; ab.4-ab.6, three posterior abdominal limbs for jumping; h. heart with 

 six pairs of ostia; or. ovary; /lep. hepatic caecum; p.ca. posterior caeca of 

 the alimentary canal; med.d.cni. median dorsal caecum; al. 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; tel. telson (cleft). 



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 ooste- 

 gites on those of the third to fifth pairs in the female (Fig. 280). The 

 alimentary canal has a single-chambered but complex proventriculus, 

 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 prin- 

 cipal organs of excretion are antenna! glands. The heart extends from 



