58 CRUSTACEA—COPEPODA CHAP. 
in the species figured, Calocalanus plumulosus (Fig. 26), from the 
Mediterranean. 
Sars makes a curious observation’ with regard to the 
distribution of certain Calanidae. He reports that along the whole 
route of the “ Fram,” 
species such as Calanus 
hyperboreus and Huch- 
aeta norwegica were 
taken at the surface, 
which, in the Nor- 
wegian fjords, only 
occur at depths of over 
100 fathoms. He 
suggests that the Nor- 
wegian — individuals, 
instead of migrating 
northwards as the 
warmer climate super- 
vened, have sought 
boreal conditions of 
temperature bysinking 
into the deeper waters. 
“wy ne Tue 
7p vii weonarernan. 
Fic. 26.—Calocalanus plumulosus, x 15. \ 
(AfteriGickbrecht) The first antennae 
of the male are asym- 
metrical, one, usually the right, being used as a clasping 
organ. 
The males of the Centropagidae, Candacidae and Pontellidae, 
besides possessing the asymmetrically modified thoracic limbs of 
the fifth pair also exhibit a modification of one of the first 
antennae, which is generally thickened in the middle, and has 
a peculiar joint in it, or geniculation, which enables it to be 
flexed and so used as a clasping organ for holding the female. 
Fam. 1.—Centropagidae.—These Copepods are very common 
in the pelagic plankton, and some of the species vie with the 
1 Norwegian North Polar Exp. Sci. Results, vol. i. part v., 1900. 
