422 Dr. H. J. Hansen on the MorplinJogij of the 



the Calanida3 are " pliylogenetically the oldest forms " among 

 the Eucopepoda) that the rudiments of the first and second 

 vairs of maxillipedes arise entirely independently one of the 

 other ; consequently they each correspond to their own pair of 

 appendages, and not to the outer and inner branches of one and 

 the same pair. Owing to the peculiarities in the structure 

 and the relative position of the maxilljB and maxillipedes in 

 the free-living and parasitic Copepods I regard the maxillae 

 as homologous with the maxillulaj, the first pair of maxilli- 

 pedes as homologous with the maxillae in the Malacostraca, 

 and the second pair of maxillipedes as homologous with the 

 maxillipedes (e. g. in the Amphipods), and, among other 

 thingvS, as exhibiting the same tendency towards mutual 

 fusion. 



12. In Argulus the swimming-feet consist very distinctly 

 of a three-jointed shatt and two branches (Kroyer). The 

 basal joint of the shaft is much shorter than the second and 

 somewhat shorter than the third. 



13. It follows from §§7-12 that toe must assume the 

 ^presence of three segments in the stem of all cleft appendages in 



Crustacea to he a primary condition ; and this number has 

 distinctly persisted, at any rate in the cases quoted. 



b. MALACOSTRACA. 

 a. Lp:ptosteaca (§§14-17). 



14. Nehalia must be assigned to the Malacostraca (Claus), 

 and in many respects it approaches the MysidjB, while the 

 Euphausiidffi, on the contrary, are very far removed from it 

 (u«V/e§26). 



15. In Nelialia hipes the shaft of the second pair of antennae 

 consists not of three (Claus) but of five segments, and the 

 fifth segment shows a tendency to he composed of two (Claus), 

 which are Avell se{)arated in Nehaliopsis ; after removing the 

 shield the first segment may be easily found by the aid of a 

 good dissecting-microscope ; this segment is somewhat short, 

 but well marked off; the fourth segment is conspicuously 

 marked off on the outer side, but is yqvj short. 



16. The limbs of the thorax consist not of seven but of 

 nine segments. In Nebalia hipes we find on the outer side of 

 the limb at the base a somewhat short but very distinct 

 segment ; after this there come the segments with the epi- 

 podite and exopodite, and finally the remainder of the limb 

 shows three distinct incisions on the inner margin and three 

 joints. (All these details are best seen in appendages laid 



