54 TAGE SKOGSBERG 



wie es bei den hoheren C y p r i d e n, wo der Endopodit keine Bedeutung hat, der Fall ist. 

 Statt dessen muB alsdann der bei der Nabrungsaufnahme zu verwendende Teil verlangert werden, 

 auch ist ihre Beweglichkeit von Nutzen, um nicht von den Bewegungen des iibrigen Beines abhangig 

 zu sein." It ought to be obvious that this assumption cannot be used as a proof of the accessory- 

 nature of the forward pointing process; as an assumption it may be taken for what it is worth. 



As a proof for the exopodite nature of the vibratory plate there has also been advanced 

 the early appearance of this organ during ontogeny, as in other Crustacean groups the 

 epipodial appendages usually appear comparatively late. We should note, however, that the 

 forward pointing process on the fifth limb is also developed rather early; in a number of forms 

 it is even more powerfully developed relatively in the larvae than in the mature individuals. 

 It is probably impossible to draw any conclusions from these facts as to the morphological value 

 of these processes. The early appearance of these two organs during ontogeny is presumably 

 due less to their great phylogenetic age than to the fact that they are both of vital importance 

 even in the early larval stages. E. KORSCHELT and K. Heider state in their ,,Lehrbuch der 

 vergleichenden Entwickluugsgeschichte der wirbellosen Thiere", p. 389, that it can by no means 

 be considered impossible that the early or late appearance of the epipodial appendages is closely 

 connected with the needs of respiration. 



No really decisive evidence in favour of either of the 

 alternatives mentioned can thus be said to have been brought 

 forward so far, nor, in my opinion, is it possible at present to 

 find any. I have myself tried to find evidence both among the facts of comparative mor- 

 phology and in embryology, but without any positive result. It seems most probable to 

 me, however, that G. W. MOller has found the most correct solution of this problem. In 

 the present treatise the vibratory plates on the fifth, sixth and sevenths limbs have conse- 

 quently been taken to be epipodial appendages. 



What was most decisive in causing me to take this view was the structure of the fifth 

 limb in the family Polycopidae. It is true that the assumption that the two distal, verruciform, 

 unjointed processes on this limb really correspond to an exopodite and an endopodite has not 

 yet been proved; it is only a postulate put forward by G. W. MtJLLER even with the addition 

 of a query, and no forms have been found so far that have enabled this statement in any way 

 to be changed into a proof. But it seems to me, however, as is pointed out above, fairly probable 

 that this assumption of G. W. MUller's is correct. It seems to be supported partly by the 

 fact that the P o 1 y c o p i d s show primitive characteristics with regard to the preceding 

 limbs, partly because both these processes seem to appear constantly in all the forms belonging 

 to this group, partly also perhaps because they are moved by special muscles in the same way. 

 If these two processes are homologous with the exopodite and the endopodite, the vibratory 

 plate must of course, as has been pointed out above, be taken as an epipodial appendage. The 

 shape of the vibratory plate in this group also seems to me to support the idea that it is of the 

 nature of an epipodial appendage. 



This view is perhaps also supported by the fact that the forward pointing process on the 

 fifth limb is developed best in a number of forms which are at the present time looked upon 



