MOUTH-PARTS OF THE PAL.EMOXID PRAWNS. 



71 



doubt upon this explanation. It may be that tlie constrictor 

 muscles of the oesophagus conduct the process. 



2. The first maxillipeds and the maxillce probably take no very 

 prominent part in manipulating the food. The feeble lobes of 

 the maxillse are in incessant movement to and from the middle 

 line as they are carried inwards and outwards by the action of 

 tJie scaphognathite. It seems not unlikely that their sole 

 function is to i^egulate the motions of the latter. The large 

 lacinia of the first maxilliped is a rather weak structure, with 

 slender silky bristles, and is not strongly moved during feeding. 

 Probably, by covering the lobes of the maxilla, it prevents them 

 from being clogged by the food. 



The pait played by the paragnatha seems to be a passive one. 



The labrum undergoes active movements, whose function is 

 probably to aid in keeping the food under the action of the 

 incisor processes. 



3. The exopodites of the maxillipeds are in constant rapid 

 motion, setting up by their activity a strong current forwards 

 fi^om the mouth, ^o doubt, this assists in carrying away the 

 exhausted water from the gill-chambers and the excreta of the 

 green glands poured out at the base of the antennte. But it has 

 also a significance in tlie feeding process. From time to time 

 particles are rejected by the second maxillipeds-, which kick them 

 violently forwards, the distal parts of the third maxillipeds at 

 the same time sti-aightening so as to admit them to the outgoing 

 stream, by which they are swept away. 



Explanation of Lettering of the Text-figttres. 



1 I., 2 I., 



llg., 



1 mocp., ' 



ap.. 

 a.r.. 



ax., 

 has., 

 b.is.. 

 b.m., 

 car., 

 cox., 

 dac, 

 d.c, 



en.. 



ep.. 



ex.. 



fl. 



gi.. 



endites or the primary segments 

 wliicli correspond to them. 



additional segment in the max- 

 illiped of Calanus. 



first and second lobes of maxilla 

 of Decapoda. 



first leg of Leander. 

 I m.vp., 3 m.vp., first, second, and 

 third maxillipeds oi Leander. 



apical lobe. 



third or additional row of seta; 

 on thoracic limb oi Nebalia. 



axis of parapodii;m. 



basipodite. 



basi-ischiopodite. 



base of mandible. 



carpopodite. 



coxopodite. 



dactj'lopodite. 



dorsal cirrus. 



endopodite. 



epipodite. 



exopodite. 



flabellum. 



gill of pob'chsete worm. 



papilla for opening of maxillary 

 gland of Stomatopoda. 



groove across paragnathum of 

 Leander. 



i., incisor process of mandible. 

 i.L, inner lacinia of maxillule of 

 Malacostraca. 

 isG.mir., ischio-meropodite. 

 I., labrum. . 

 I.', side lobe of labrum. 

 l.r., lateral row of setae. 

 m., molar piocess of mandible. 

 m.r., marginal row of setse. 

 mer., meropodite. 



«., notch on paragnathum to 

 receive endopodite of max- 

 illule. 

 o.h, outer lacinia of maxillule of 

 Malacostraca. 

 paragnathum. 

 palp of mandible, 

 precox.i. 

 proepipodite. 

 propodite. 

 pro7dac., pro-dactj-lopodite. 

 )'., r.', r." , ridges of segments of first leg 

 of Leander. 

 s. r., second side row of setae. 



s., subapical lobe. 

 V.C., ventral cirrus. 

 X., so-called " exopodite " of 

 Triarthriis. 



p.m., 



pr.c.r. 



pr.ep., 



pro.; 



