SCHIZOPODA. 



469 



spermatozoa are filiform in Mysis, but in the Hemitropha they 

 are elliptical cells and, as in the Decapods, are transferred to 

 the female in spermatophores. In the Holotropha the vasa 

 deferentia opens on conical eminences on the bases of the last 

 thoracic legs. These projections are absent in the Hemitropha, 



FIG. 291. Three stages in the development of Euphausia. A metanauplius (after Metsch- 

 nikoff) ; B Calyptopis stage (after Glaus) ; C later Calyptopis stage (after Claus). 1 and 2, 

 in A and B, first and second antennae ; 3 mandible ; 4 and 5 first and second maxillae ; /, 

 in C, first maxillipeds ; a^-a^ first to fifth abdominal segments ; a& sixth abdominal limbs ; 

 ab abdomen ; an anus ; fs frontal organ ; o upper lip ; th thoracic segments ; u lower lip. 

 (From Korschelt and Heider.) 



but the two anterior pairs of abdominal feet are here modified 

 as copula tory organs. In the Mysidae the males are distinguished 

 by the full development of the swimmerets, and in Siriella by 

 the presence on the latter of the peculiar branchial (?) appendages 

 noted above. In all, the males are distinguished by the structure 



