THE COFEPODA 



77 



scheme of classification, are widely separate from each other, and 

 especially the fact that the geniculation occurs in the same place 

 in some, probably in all cases, suggests that this character is a 

 primitive one for the whole group, and that its absence is a 

 secondary modification. This view is supported by the interesting 

 fact observed by Clans, that in some Gymnoplca Anipliaskandria 

 a trace of this modification persists in the coalescence of the 

 twentieth and twenty-first segments of the antennule in the male, 



Fig. 43. 



A, clasping antennule of male Ccn^ropn/jcsij/jucHS (Gymnoplca, Heterartlirandria) ; *, position 

 of tho hin^e-joint. li, last pair of thoracic limbs of the same, en, endopodites ; ex, exopodites, 

 that of the right side modified as a chelate f,Tasping organ. (After Sars.) 



and that in some cases this coalescence only appears in the antennule 

 of one side as in the allied Heterarthrandria. 



The antennae, like the antennules, preserve in many Euco- 

 ])epoda the general structure and the natatory function which 

 they have in the nauplius. They are most fully developed 

 in the Gymnoplea, Avhere they consist of a protopodite of 

 two segments, an endopodite of tAvo segments, and a multi- 

 articulate exopodite, and bear numerous long natatory setae (Fig. 

 41, B). In the Podoplea the natatory function is less well marked, 



