•2C< T.VIK SKOilSKKlid 



Tlu' |<nsl-()ral liihlis til the ( ) s t r a c o d s arc. as lias jiisl Ihmmi inMiitcd out. cxT'ccdintily 

 iu\iltiforni; tin- same limit i)ltcn appears in muIi (lilTcrciit types in the different <;nm]>s that 

 a certain hoiuoli)gizatiim of its diftVrent parts seems to be almost hopeless. As a mattei' 

 of fact the Ostracod jirouj) comprises such heterop;eneous elements that one cannot expect 

 a jiriori to find any far-reaching morphological agreement between actually homologous organs. 

 Innervation, musculature, the number of joints, the bristle equipment, in other words the 

 anatomical characters that arc concerned, often completely fail to give a certain clue to the 

 homologization. 



A 1 t h o u g h facts obtained from comparative m o r p h o 1 o g y 

 a n (1 e m b r y o 1 o g y have a s f a r a s possible li e e n taken into c o n- 

 s i d e r a t i o n in discussing these ]> r o b 1 e m s, t h e determining factor 

 has been, under these circumstances, the position of the parts 

 dealt wit h. their r e 1 a t i v e p o s i t i o n t o e a c h o t h e r a s well as t h e i r 

 position in relation to the 1 i m 1) t a ]< en as a whole. The r e s u 1 1 s 

 of h o m o 1 o g i z a t i o n s carried out on so slight a basis as the 

 positions must, of course, be both uncertain and unsatisfactory 

 in manv cases*; this is still more so as the situation of the different parts of the limbs 

 is by no means constant. 



G. W. MOller, the only author who has discussed this problem in detail for the () s t r a- 

 c d s, does not show quite clearly what principles he has followed in working it out. But 

 this writer seems, at least in some cases, chiefly to have followed the last principle put forward 

 by me above, i. e. the positions of the different parts has been taken by this author too as 

 the determining factor. In other cases, on the contrary, other principles have been the dominant 

 ones for this writer. As a result of this he has in many cases, as is shown below, arrived at 

 results quite different from those put forward in this work. 

 Srmnii nnii-nna. Sccoud antenna: — With regard to this limb I follow almost entirely the 



terminology found in G. W. Muller's large treatise of 1894. According to this author this 

 antenna is a biramous limb, consisting of a protopodite, an exopodite and an endopodite; on the 

 other hand there are no epipodites and endites at all. The protopodite is sometimes single- 

 jointed, sometimes two-jointed, sometimes it even has an indication of a third joint. The 

 exopodite and endopodite are developed very differently in different groups; sometimes both 

 these branches are well developed, as in Thaumatocypris, the P o 1 y c o p i d s and the 

 Cytberellids, sometimes the exopodite dominates decidedly over the endopodite, as, for 

 instance, in the C y p r i d i n i d s and most of the H a 1 o c y p r i d s; sometimes the exopodite 

 is very much reduced, the endopodite on the other hand, very large and powerful, as in the 

 Cx'prids, Darwinulids, Nesideids and C y t h e r i d s. 



Before G. W. MCller it was assumed that the natatory branch in the C y p r i d i n i d s, 

 Halocyprids and Polycopids represented the endopodite, the other branch the 



• The diffirulty of carrying out a terminology, based on a (ertaiii homologization. for the different parts of I lie 

 Ostracod limbs, corresponding to that which has been accepted for other Crustacea may perhaps seem to justify tlie use. 

 at least for the pre.sent, of a quite neutral terminology for this group. The reason why this method has not been chosen 

 in the present work is that because, in my opinion, it would only inrrease Ihe confusion in these fpieslions. 



