Srciiiiil iinli-niiii . 



■n; ■\\\v,v. sk()c.si!ioi{(; 



Tlie ]jost-()i;il limbs ol tin' O s t r a cods are, as has just bi-oii pointed out, exceediiigl>- 

 iiniltiform; the same limb often appears in such different types in the different groups that 

 a ct'rtain homologization of its different parts seems to be almost hopeless. As a matter 

 of fact the Ostiacod group comprises such heterogeneous elements that one cannot expect 

 a priori to find any far-reaching morphological agreement between ac^tually homologous organs. 

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

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

 homologization. 



A 1 1 li o u g h facts o b t a i n e d f r o m comparative m o r p h o 1 o g y 

 and embryology have as far as possible been taken into con- 

 sideration i ti discussing these p r o b 1 e m s, t h e determining factor 

 has been, under these c i r c \i m s t a n c e s, the position of the parts 

 dealt with, their relative position to each o t h e r' a s well as their 

 position in r e 1 a t i o n to the 1 i m b taken as a whole. The results 

 o f li o m o 1 o g i z a t i o n s c a r r i e d out on so s 1 i g li t a basis a s t li e 

 positions m u s t, of course, be both u n c e r t a i n and u n s a t i s f a c t o r y 

 i n m a n v cases *; this is still more so as the situation of the different parts of the limbs 

 is by no means constant. 



(t. W. MUIjLKH, the only authoi who lias discussed this problem in detail for the s t r a- 

 c o 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 ])ut 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. 



Second antenna: — With regard to this limb I follow almost entirely the 

 terminology found in G. W. Mullbr'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 e})ipodites and endites at all. The protopodite is sometimes single- 

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

 exopodite and endopodite are developed very differently in different groups; sometimes l)oth 

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

 C!y 1 1) r r el li d s, 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 Halo 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 

 C y ]) r i d s, D a r w i n u 1 i d s, N e s i d e i d s and C y t h e r i d s. i 



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

 ilalocy|)rids and Polycopids represented the endopodite, the other branch the 



* The (liriiiully of carrying out a lerminology, based on a ( crlaiii homologization, fur llic iliflVroiit parts of llir 

 Ostrrii-0(l lliiil)s, corrpsponding to that which has been acceplod lor other ("rustacea may [lerhaps seem to justify the use. 

 al b^asl lor (he iircsenl, of a quite neulrat terminology for tliis group. The reason why tliis metliod has nol been cliosen 

 in \]\f prcscnl worl; is thai liecanse. in my opinion, il wcmld (inly increase the c<inr\ision in these quc-;tiuas. 



