Memoirs: On the Ciliary Mechanisms and Interrelationships of Lamellibranchs: Latero-frontal Cilia of the Gill Filaments and their Phylogenetic Value

摘要: Certain Lamellibranchs have the latero-frontal tract composed of large complex ‘cilia’, here called eu-latero-frontal cilia , together with subsidiary ones, termed pro-latero-frontal cilia. This type occurs in some or all three families Protobranchs (there is doubt as to presence families), and Mytilidae probably Trigoniidae (fixation too imperfect for identification cilia) among Filibranchs, marine Eulamellibranchs obtainable at Plymouth, fresh-water families, Dreissensiidae, Sphaeriidae, Unionidae, Mutelidae, Aetheriidae. A list species investigated given. Other Lamellibranchs, which were previously considered lacking cilia, been found possess small ones only, difficult observation, micro-latero-frontal These occur Arcidae, Anomiidae, Pteriidae, Pectinidae, Spondylidae, Limidae, Pinnidae, are inferred be present Amussiidae, Vulsellidae, Isognomonidae, certainly absent. examined In one family, Ostreidae, moderate-sized anomalous para-latero-frontal present. bivalves having arrangement various ciliary tracts, frontal, latero-frontal, lateral fairly constant, notable exceptions being a Protobraneh, Nuculana, Filibranch, Trigonia . tracts seems more less constant. The homology types discussed. composition ciliated has stable character, and, it correlated other characters, taxonomic value. It suggested that variations constitution tend show Ridewood9s (1903) classification does not express genetic affinities, he himself conceded, nor Pelseneer9s (1911) entirely, order Filibranchia, orders Bleutherorhabda Synaptorhabda monophyletic. Families possessing appear closely related, form group, which, certain modifications, corresponds ‘the Aviculidae their allies’, ‘sedentary’ branch established by palaeontologists, Jackson Douville respectively, largely on shell characters. Thus laterofrontal gill filaments supports findings palaeontologists regard this group. Unfortunately neither proposed formal name relationship forms evolution within group eulamellibranchiate synaptorhabdic One must included account its either Pteriacea Pectinacea (based evidence) moderatesized, paralatero-frontal differ respects from characteristic majority Laraellibranchia, presumed arisen independently. Common characters characterized possession addition are: (1) prodissoconch, Arcidae excepted; (2) byssal fixation; (3) considerable free posterior region axes; (4) development muscles axes, Ostreidae (5) method division pallial cavity, (6) gills without supra-axial extension outer demibranch; (7) longitudinal currents ventral edge both inner demibranchs; opposed frontal lamellae frequently same filament, Pinnidae (8) absence sutures, (9) fold mantle margin characteristically well developed, especially swimming forms; (10) insertion retractor distance edge, (11) tendency members, except lie right valve; (12) abdominal sense organs adductor muscle; (13) intercommunication auricles, Anomiidae excepted. Two groups Lamellibranchia provisionally, namely Group I, Macrociliobranchia, including Protobranchia (Pelseneer), Filibranchia (emended include only Mytilacea Trigoniacea), Eulamellibranchia (Pelseneer, 1911), Septibranchia (Pelseneer); II, Microciliobranchia, Pseudolamellibranchia, emended sub-orders Arcacea (excluding Trigoniidae), Anomiacea, Pteriacea, Pectinacea, Ostreacea. Macrociliobranchia will need revision, very probable (emended), if Eulamellibranchia, still