Limbs and Mouth-parts of Crustaceans and Insects. 421 
8. In Limnetis, Estheria, &c. we find a similar structure ; 
but in conseque nce 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 Hislopi: “The 
endopodite consists of six imperfectly defined segments, each 
of which is produced 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 
Calanus, the shaft of the second pair of antenne is three- 
jointed (Kréyer) and in the mandibles the exopodite proceeds . 
trom the third segment, since after the actual mandible (first 
segment) there is found a small segment (described by 
Kréyer) which is usually overlooked. In the large Meta- 
nauplius stages I also succeeded in discovering three segments 
in the shaft of the second pair of antenne and of the man- 
dibles. In Setella the three segments in the shaft of the 
second pair of antennz can be seen without difficulty. 
11. In a series of large larvae (Metanuuplius stage) be- 
longing to the family Calanide I have found antennules, 
antennee, and mandibles, developed as in the Nauplius, 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, maxille, first and second pairs of maxillipedes, and 
two pairs of swimming-feet. There ts some considerable 
distance between the points of origin of the rudiments of the 
Jirst 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 which extends across the ventral surface as a 
faint streak between the two rudiments. That my interpre- 
tation of these rudiments is correct 1s borne out by the fact 
that I possess specimens of the following stage, with all five 
pairs of appendages perfectly well developed, and only two of 
them are swimming-feet. I consider therefore that I am 
entitled definitely to conclude (indeed, according to Grobben, 
