292 



ZOOLOGY 



The mandible carries a three-jointed palp, and the maxilli- 

 pedes fuse in the middle line to form an under lip. The bases 

 of the thoracic Umbs of the females bear on their inner surface 

 a process, probably the epipodite, which projects towards the 

 middle line, and with its neighbours forms the brood-pouch. 



Fig. 168. — The mouth appendages of Gawmmrus neglectus. 

 From Leiickai-t and Nitsche, after 6. 0. Sars. 



1. The mandihle. 



2. Its palp. 



3. 1st maxilla. 



4. 2nd mazUla. 



5. Maxillip«de of each side together forming an under lip. 



A little distal to this, but on the same surface, is a vascular 

 process, the gill. The heart stretches through the thorax, and 

 has usually a pair of valves in the second, third, and fourth 

 thoracic segments. A well -developed "fat -body" is often 

 present, lying amidst the viscera. 



Certain Amphipods, as Gammarus, Orchestia, Talitrus, 

 Caprella, etc., have two caeca which open into the alimentary 

 canal at the junction of the mid and hind gut. These caeca, 

 which stretch either backwards or forwards, contain numerous 

 concretions in their walls. They have been compared to the 

 Malpighian tubules of the Tracheata, but there is no certain 

 evidence to show that they excrete nitrogenous waste matter 



