50 



TAGE SKOGSBERG 



Seventh limb. 



Cypridae, 



Danvinulidae, 



Nesideidae and 



Cylheridae. 



Halocypridae. 



('yi>ridinid(ir. 



of bristles that is found in most cases on the posterior edge of the protopodite and that was 

 taken by me above to be a remains of a vibratory plate appears, according to a statement on the 

 same page, to belong to a reduced vibratory plate. This assumption has later been adopted 

 by G. W. MULLER. Neither of these two authors has tried, however, to give any proof for 

 their views. — With regard to the morphological value of the vibratory plate — just as in the 

 case of the same organ on the fifth limb — we find two different views in the literature; most 

 ■^lyj-iters — if they have any opinion in this matter — take it to be an exopodite; G. W. MOller 

 assumes that it is homologous to an epipodial appendage. The backward pointing part of this 

 limb, the part which is rod-shaped in Halocyprids, Cyprids, Darwinulids, 

 N e s i d e i d s and C y t h e r i d s, is taken by all writers to be an endopodite. With regard 

 to this limb in the family Cypridinidae G. W. MUller assumes, 1894, p. 68, that the proximal 

 joint, with two endites, corresponds to the protopodite, the three distal joints to the endopodite. 

 Curiously enough G. W. Muller seems to have been very sure about the extension of the 

 protopodite. Thus he writes on this point, loc. cit. „so ist es wohl unzweifelhaft, daB bei 

 Cypridina das 1. Glied, welches an seinem Vorderrand 2 Hocker mit Borsten hat, als 

 Stamm . . . zu bezeichnen ist". The reason why G. W. MOLLER and I have arrived at 

 somewhat different ideas as to the morphological value of this limb in the family Cypridinidae 

 is probably to be found in our different explanations of the fifth limb in this family. Just as 

 I have done above, G. W. MulleR has completely applied the homologization of the fifth limb 

 to the sixth one. Other investigators too have assumed that the distal part of the sixth limb 

 in the C y p r i d i n i d s corresponds to the endopodite, but they have not indicated the 

 exact boundary between the protopodite and the endopodite. 



Seventh limb: — This is not found in the Polycopidae and Cytherellidae. 

 The families Cypridae, Darwinulidae, Nesideidae and Cylheridae: In these families the 

 seventh limb shows such a far-reaching agreement witli the two preceding limbs that it seems 

 to me that there are no serious objections to applying quite the same homologization to this 

 limb as well. According to the first method of explanation the backward pointing rod- 

 shaped branch is to be considered as an exopodite, according to the other it is to be taken 

 as an endopodite and the part situated proximally of this branch is homologous to the 

 protopodite. No organ is ever developed that could be considered as an endopodite accor- 

 ding to the first method of explanation. The vibratory plate, which according to the first 

 explanation is to be homologized with an epipodial appendage, according to the second with 

 the exopodite, is always reduced; it can, however, be traced in most cases as single bristles 

 on the posterior side of the protopodite, situated sometimes proximally, sometimes distally. 

 No endites are developed. 



It seems impossible to decide with certainty at present whether the very much reduced 

 seventh limb in the Halocyprids is to be taken as a protopodite -+- an exopodite or only 

 as an exopodite, according to the first method of explanation, or as a protopodite -f- an 

 endopodite or only as an endopodite, according to the second. 



It is rather probable that the peculiar worm-like cleaning organ in the family 

 Cypridinidae is also to be taken as a rod-shaped limb consisting of a protopodite and 



