4S 



I'vdH siv'OftSBEua 



According to the second aiethod of explanation the last-mentioned collection of bristles is to 

 be considered as a remains of the exopodite, the two distal joints presumably represent the 

 endopodite; the protopodite has the same extension as according to the former method of 

 explanation; cf. fig. VII: 2. 



The collection of bristles that is in most cases to be found on the posterior edge of the 

 part that has been explained as a protopodite is thus, in my opinion, to be considered as the 

 rudiment of a homologon to the vibratory plate on the preceding limb. This assumption seems 

 to be supported both by the position of these bristles and by the fact that they are sometimes 



I'ic MI. — Sixth limb nt ('y/jridiiin medilerrnnea O. Costa (From G. W. Mullkr. 189'i). 1. According to ..the lirsl 

 mclhod of exphvnatioii". 2. According to „tlu' second method of explanation" the first alternative. 



attached to a lobe-like process, though the latter is small. It seems, at least at present, to be 

 impossible to prove this assumption. For the cause of a possible reduction of this vibratory 

 plate see G. W. Mt)LLER, 1894, p. 198. 



There is no part that might be explained as an endopodite according to the first 

 iiietiiod of explanation* (as in the fifth Umb). 



We must note the uncertainty that, in my opinion, exists in both the methods of explanation 

 described above, with regard to the boundary between the protopodite and the branch situated 

 (listally of this. Perhaps only the proximal joint, the one that in most cases is characterized by ha- 

 ving two bristle-bearing endites on the anterior edge, is to be considered as a protopodite. Or does 

 the exopodite (or the endopodite as the case may be) consist only of the large end joint? These are 

 questions that probably cannot be decided with certainty, at least at present. Of the three 

 alternatives mentioned above it seems to me, however, that the first, namely that the protopodite 

 comprises the two proximal joints, is the most probable and it has been adopted in the present 

 work. This statement is supported, it seems to me, by a comparison between the fifth and 

 sixth limbs. It may be sufficient to refer to a comparison between the schematic figures, 

 reproduced above, of the fifth limb in the sub-family Cypridininae (figs. IV: 3, 4) and the figures, 



* It seems Id nil- iin[iio|.;il.lr lli.il il is re]ir-eseiite(l liy llir jiriiit next In tlie oiitei- (inc. t^f. the emliryology of 

 tlie limb below. 



