68 



TAGE SKOOSBEBG 



fifth limb. Fifth limb: — This appendage would have been of about the same type as that 



of Macrocypru, a recent genus belonging to Cyfridar. l)ut it was probably furnished, however, 

 with a vibratory plate of about the same type as that wliich characterizes this limb in the 

 H aloe vpr ids. Its protopodite would have been fairly large and to a rather great extent united 

 to the bod\\ Distallv-anteriorly the ])rotopodite woidd have been furnished with a short 

 process (explained by G. W. MCllbr as the exopodite). Its exopodite*, which pointed backwards 

 and was fairly long, was four-jointed, with a small end-joint armed with three bristles. This 

 limb woidd have been used partly in taking up food and partly as a locomotory organ „(An- 

 klammern?)". During its further development sometimes one and sometime the other of these 

 two functions was prominent. \Mien the former function predominated the forward pointing 

 process on the protopodite was almost always completely reduced. When the taking up of 

 food became the principal function of this limb it was necessary, owing to the reduction of the 

 forward pointing process, for the limb to move forward to the boundary between the head and 

 the trunk of the body (Cypridae) or even right up to the hypostome (Cypridinidae and Halo- 

 cypridae), so that owing to its position it came to look like a limb of the head. In the males 

 of the ancestors of the families that are placed by Gr. W. MOller in one group under the name 

 of Podocopa the exopodite of this limb would have been already developed as an auxiliary 

 organ in copulation. 

 Sixtii ittiih. The sixth limb would in the Protostracods have borne the closest 



resemblance to this appendage in the females of the Halocyprids. This limb of the 

 Cyprids, Darwinulids, Nesideids and Cytherids has been adapted to 

 a crawling life and especially on account of this has been lengthened. With regard to this limb 

 in the C y p r i d i n i d s G. W. MOLLER says that it is ,,nichts weniger als eine urspriingliche 

 Form". „Bei den Polycopiden ging in Folge der starken Reduction der KorpergroBe 

 dieses, sowie das folgende Beinpaar verloren." 

 Seventh limb. Seventh limb: — This appendage, which has two principal functions in recent 



forms, namely those of a cleaning or a crawling organ, was already a cleaning organ in the primitive 

 forms and had about the same type as in the recent Cyprids. We find it developed as the 

 most complete cleaning organ in the Cypridinids; its chief task is to keep the brood- 

 chamber clean. In the Halocyprids it was originally a more perfect cleaning organ 

 than in the recent Cyprids; it was then reduced, „in Folge des Aufgebens der Brutpflege?". 

 In the Nesideids and Cytherids it became exclusively an organ of locomotion. 

 Vibraionj plates. Vibratory plates: — These are arranged as follows in the recent Ostracods: 



In Cypridinidae and Polycopidae on the fifth limb, in Haiocypridae on the fifth and sixth limbs, 

 in other Ostracods they are situated farther forward, on the mandible and the maxilla, 

 less frequently on the fifth limb as well, in exceptional cases (CytJierella) on the sixth limb. 

 G. W. Mt'LLER assumes that the Protostracods had vibratory plates on the fifth and 

 sixth limbs of about the same type as in the recent Halocyprids or perhaps on the fifth, 

 sixth and seventh limbs, ^^^len these organs were reduced on the^posterior limbs similar ones 

 would have appeared „compensatorisch an Mandibel und Maxille". As evidence for this opinion 



"^ Eiidopodite according to lliis author's interpretation. 



