studies on marine Ostracods 



87 



seems to be quite unsupported. With regard to this it ought to be enough to point out that 

 this limb is not developed as a seizing organ in two of these families, namely Nesideidae and 

 Cytheridae, and that the sixth limb in the males of Cytherella even shows a closer resemblance 

 to the fifth limb of the C y p r i d s than does their fifth limb. 



It is possible that the position of the fifth limb of C y p r i d i n i d s and H a 1 o c y- 

 p r i d s, where it is placed far forward, is, contrary to G. W. MtlLLER's view, to be considered 

 as original. This assumption of G. W. Muller's is, of course, connected with his supposition 

 that the limb corresponding to te second maxilla of other Crustacean groups has disappeared 

 in the Ostracods. 



Sixth limb: — There is the same uncertainty with regard to this limb as with the 

 preceding one. The assumptions that the foliaceous type of the C y p r i d i n i d s is original 

 and that the rod-shaped type is the most primitive are opposed to each other in this case as 

 well. The fact that with regard to this limb too there is a very great agreement between 

 the Halocyprids on the one hand and Cyprids, Darwinulids, Nesideids 

 and Cytherids on the other makes the assumption that the resemblance between these 

 limbs is due to convergence seem very improbable. 



It seems to be impossible to make any detailed statement at present as to the cause 

 of the disappearance of this and the following limb in Polycofidae. G. W. MtiLLER assumes 

 that it was due to the smaUness of these forms. It is to be noted that these limbs are also 

 reduced in the C y t h e r e 1 1 i d s, although these are comparatively large forms. 



Seventh limb: — Contrary to the two preceding limbs the seventh one never has a 

 foliaceous type in the recent Ostracods. In Cyprids, Darwinulids, Nesi- 

 deids and Cytherids it is of about the same type as the fifth and sixth limbs ; in the 

 Halocyprids it is certainly short, but all the same it is rod-shaped; in the C y p r i- 

 d i n i d s, the group in which the fifth and sixth limbs are of the foliaceous type, it is developed 

 as a long, vermiform annulated appendage. (In the Polycopids and Cytherellids 

 this appendage is, as we know, not found at all.) These facts seems to support G. AV. MCller's 

 assumption that this limb was originally of the rod-shaped type; it was perhaps, as this 

 investigator assumed, of about the same type as in the recent C y p r i d s. This fact may 

 also perhaps be considered to support the assumption that the rod-shaped type was also 

 original for the two preceding limbs. 



Was this limb developed as a crawling limb in the Protostracods or did it act 

 as a cleaning organ? G. W. MtJLLER assumes, as we have seen above, that it was used as a 

 cleaning organ; other investigators, e. g. G. Alm, 1915, assume that it only adopted this function 

 later. Which of these views is to be considered as correct? 



G. Alm puts forward the following reasons for his view (pp. 18 — 21): In the Nesi- 

 deids and Cytherids this appendage is used as a crawling limb, not as a cleaning organ. 

 In the Darwinulids it is possibly used as a cleaning organ, but probably, at any rate, 

 this fimction is only to be considered as secondary, crawling being the most important function. 

 In the Cyprids we find in the lower forms that this appendage, although developed as a 

 cleaning organ, ,,nach ihrer Lage zu urteilen sowohl als Bein wie als PutzfuC anwendbar ist" 



Sixth tiinh. 



Seventh limb. 



