MOUTH -PARTS OF THE PAL.EMONID PRAWNS. 



71 



doubt upon this explanation. It may be that the constrictor 

 muscles of the oesophagus conduct the process. 



2. The first maxillipeds and the maxilla? probably take no very 

 prominent part in manipulating the food. The feeble lobes of 

 the maxillae are in incessant movement to and from the middle 

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

 the scaphognathite. It seems not unlikely that their sole 

 function is to regulate 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 part 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 

 from the mouth. No 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 antenna?. But it has 

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

 particles are rejected by the second maxillipeds, w 7 hich kick them 

 violently forwards, the distal parts of the third maxillipeds at 

 the same time straightening so as to admit them to the outgoing 

 stream, by which they are swept away. 



Explanation of Lettering of the Text-figures. 



1-8, endites or the primary segments 

 which correspond to them. 

 9, additional segment in the max- 

 illiped of Calanus. 

 1 I., 2 I., first and second lobes of maxilla 

 of Decapoda. 

 1 Iff., first leg of Leander. 

 1 mxp., 2 mxp., 3 mxp., first, second, and 

 third maxillipeds of Leander. 

 ap., apical lobe. 



a. r., third or additional row of seta j 



on thoracic limb of Nebalia. 

 ax., axis of parapodium. 

 has., basipodite. 



b. is., basi-ischiopodite. 

 b.m., base of mandible. 

 car., carpopodite. 

 cox., coxopodite. 

 dac, dactylopodite. 



d.c, dorsal cirrus. 



en., endopodite. 



ep., epipodite. 

 ex., exopodite. 

 ji., flabellum. 

 g., gill of polychsete worm. 

 gl., papilla for opening of maxillary 



gland of Stomatopoda. 

 gr. s groove across pavagnathum of 



Leander. 



i., 

 i.L, 



isc.mir., 

 k, 



v, 



l.r., 

 m., 

 m.r., 

 mer., 

 n„ 



o.L, 



V; 

 p.m., 



pr.cx. 



pr.ep., 



pro., 



pro.dac, 



r., r. r , r." , 



s. r., 

 s., 

 v.c, 



X., 



incisor process of mandible, 

 inner lacinia of maxillule of 



Malacostraca. 

 ischio-meropodite. 

 labrum. 



side lobe of labrum. 

 lateral row of setse. 

 molar process of mandible, 

 marginal row of seta?, 

 meropodite. 



notch on paragnathum to 

 receive endopodite of max- 

 illule. 



outer lacinia of maxillule of 



Malacostraca. 

 paragnathum. 

 palp of mandible, 

 precoxa. 

 proepipodite. 

 propodite. 

 pro-dactylopodite. 

 ridges of segments of first leg 



of Leander. 

 second side row of setae, 

 subapical lobe, 

 ventral cirrus. 



so-called " exopodite " of 

 Triartlirns. 



