Limbs and Mouth-parts of Crustaceans and Insects. 421 



8. In Limnetisj Estheria, &c. we find a similar structure ; 

 but in conseque nee of the delicacy of the integument of the 

 appendages the difference between the chitin of the seg- 

 ments and the articulations is more or less indistinct. 

 According to G. O. Sars, in Cyclestheria llislopi : " The 

 endopodite consists of six imperfectly defined segments, each 

 of which is produc ed on the inner side as a rounded setiferous 

 lobe .... the epipodite apparently issuing from the outer 

 side of the second segment of the stem .... the exopodite 

 originating immediately below the epipodite, from the outer 

 side of the third segment of the endopodite." 



9. Before the exopodite and epipodite, which are both 

 present in Branchipus, there arises a very long and broad 

 (partially cleft) plate on the outer side of the first segment. 

 It has been shown by L. Lund (Nat. Tidsskr. ser. 3, 7 Bd., 

 1870) that a similar plate exists in Cladocera. 



10. In the most highly developed Copepods, such as 

 Calamis, the shaft of the second pair of antennaj is three- 

 jointed (Kroyer) and in the mandibles the exopodite proceeds 

 from the third segment, since after the actual mandible (first 

 segment) there is found a small segment (described by 

 Kroyer) which is usually overlooked. In the large Meta- 

 naupUus stages I also succeeded in discovering three segments 

 in the shaft of the second pair of antennae and of the man- 

 dibles. In Setella the three segments in the shaft of the 

 second pair of antennae can be seen without difficulty. 



11. In a series of large larva [Metanauplius stage) be- 

 longing to the family Calanidse I have found antennules, 

 antennae, and mandibles, developed as in the MaupliaSj and 

 behind these five distinct but small pairs of plates, which are 

 the rudiments of five pairs of appendages and of which only 

 the two last show an indication of cleavage ; these rudiments 

 are consequently, to give them the designations applied by 

 authors, maxillae, first and second y)airs of maxillipedes, and 

 two pairs of swimming-feet. There is some considerable 

 distance between the points of origin of the rudiments of the 



first and second pairs of maxillipedes, which are therefore 

 entirely independent one of the other; indeed we even see 

 on the dorsal surface and on the side of the animal a distinct 

 articulation wliich extends across the ventral surface as a 

 faint streak between the two rudiments. That my interpre- 

 tation of these rudiments is correct is borne out by the tact 

 that 1 possess specimens of tlie following stage, with all five 

 pairs of appendages perfectly well developed, and only two of 

 them are swimming-feet. 1 consider therefore that I am 

 entitled definitely to conclude (indeed, according to Grobben, 



