262 A HISTORY OF RECENT CRUSTACEA 
distance from the apex, but generally reaching much 
beyond it. Luminous globules are generally present on 
various parts of the animal. The heart is furnished with 
six pairs of lateral slits or venous openings. The develop- 
ment is complex, the larva after hatching passing through 
the Nauplius- and Zoéa-stages. 
Eight genera are included in this family, three of which 
are represented in the British Fauna. 
Huphausia, Dana, 1852, which means ‘a bright light,’ 
was so called in reference to the luminous character which 
all the species of this genus share with most others in the 
same family. This genus is distinguished from the rest 
by having the last two pairs of legs quite rudimentary, 
although the branchie are well developed. By the nume- 
rous species it is almost universally distributed. It is 
pelagic in habit, that is to say, its members occupy tbe 
surface of the ocean when it suitsthem. They may or may 
not descend to great depths, but often, and especially at 
night time, they are to be found in great profusion at the 
surface. Huphausia pellucida, Dana, a colourless species, 
was met with ‘in almost every tract of the ocean traversed 
by the Challenger, and has also been taken in the Medi- 
terranean and off the coast of Norway. Huphausia superba, 
Dana, from the Antarctic Sea, has its whole body, except 
the legs and branchiz, tinged with a brilliant red. The 
luminous globules in these animals were at one time sup- 
posed to be accessory eyes, but Sars regards them as con- 
stituting ‘a very complicated and peculiarly developed 
luminous or phosphorescent apparatus.’ They are ‘ very 
conspicuous in the living animal by reason of their beauti- 
ful red pigment and glistening lustre.’ The pigment coats 
only the hinder half of the globule, which is filled up with 
cellular matter enclosing a bunch of iridescent fibres, while 
the front hemisphere is quite pellucid and contains a highly 
refractive lenticular corpuscle. This last is supposed to 
act ‘as a condenser, producing a bright flash of light, the 
direction of which admits of being changed at the will of 
the animal, by simply rolling the organ by means of its 
muscular apparatus,’ 
