THE COPEPODA 



79 



pletely developed in the Gymnoplea and some Harpacticidae, in 

 which endopodite, exopodite, and epipodite are distinct, and the 

 protopodite is produced internally into a large masticatory lobe and 

 two smaller distal lobes (Fig. 9, 

 A, p. 13). In the Cyclopidae 

 the epipodite has vanished, the 

 exopodite and endopodite are 

 very small, and only the large 

 masticatory process of the proto- 

 podite persists. In many Har- 

 pacticidae and in the other 

 families the maxillula undergoes 

 various degrees of reduction. 



The two pairs of appendages 

 succeeding the maxillulae are 

 commonly designated the outer 

 (or anterior) and inner (or 

 posterior) maxillipeds, and were 

 for long considered to represent 

 the separated rarni of a single 

 pair of appendages. This in- 

 terpretation was put forward 



T /-NM i t i ,v , A, Acontiotthorus scutatus, 9. from the side, 



by tlaUS, Who tOUnd that, 111 x 50 . Most of the appenda-.-s are omitted! 



tVip mpti Timinlin <J stacrp nf *> suctorial siphon; vi, the rudimentary sixtli 



Sta S 6 ' pair of thoracic limbs ; ! + ->, the coalesced tirst 



CudopS and Other forms, the !m<1 second abdominal somites ; 4 + :j, the fourth 



, . , abdominal somite coalesced with the telson. 



tWO appeared tO arise trom a (After Giesbrecht.) U, larva of Ithincalanus 



cino-lp rnrlimpnt Hm<?pn limv ""<">"" ' ' last metanauplins stage. Tlie outline 



single ruun ,nt. nanben, now- of tto body * seen from abova The first three 

 ever, has discovered, and the i' !lirs "f appenda-es are omitted, but the rudi- 



ments ot the posterior appendages are seen by 



observation has been confirmed transparency through tiie bodv. mi", maxillae ; 

 1 n- \ i,i iu r<l lnx Pi maxillipeds, separated from the maxillae 



by Giesbrecht and by Llaus by the line Penning 4Qie first thoracic Mmdte ; 



that in the larvae of />/"> (irs t and second pairs of swimming-feet.' 

 llldO I (After Giesbrecht.) 



certain marine Gymnoplea 



(Eucalanus, Ekincalanus, Pontella, etc.) in which the body is more 

 elongated than usual, the rudiments of the two appendages are not 

 only quite distinct, but are separated from each other by the suture 

 line which marks off from the head the so-called first thoracic 

 somite (Fig. 44, B). The " outer (or anterior) maxillipeds " are 

 therefore the maxillae, while the inner (or posterior) pair, for which 

 the name maxillipeds may be retained, must be regarded as the 

 first of the thoracic series, and the somite corresponding to them 

 is, at least in some cases, coalesced with that which bears the first 

 pair of swimming -feet. The maxilla in its most fully developed 

 form consists of a flattened and shortened axis of, at most, eight 

 segments, of which the first and second each bear two, and the 

 third a single endite (Fig. 41, C). In the Gymnoplea this appendage 

 is beset with plumose setae, which act as a net in collecting food- 



