Ill PODOPLEA—ISOKERANDRIA 69 
Nicothoe and some of the Dichelestiidae’ have more numerous 
joints. In most of the Dichelestiidae, however, the number of 
joints is less than seven and practically equal in the two sexes. 
TRIBE II. ISOKERANDRIA. 
The first antennae are short, similar in the two sexes, and 
are never used by the male as clasping organs. This function 
may be subserved by the second maxillae. 
Fams. ONCAEIDAE, CORYCAEIDAE, LICHOMOLGIDAE, ERGA- 
SILIDAE, BOMOLOCHIDAE, CHONDRACANTHIDAE, PHILICHTHYIDAE, 
NEREICOLIDAE, HERSILIIDAE, CALIGIDAE, LERNAEIDAE, LERNAE- 
OPODIDAE, CHONIOSTOMATIDAE. 
The families Oncaeidae and Corycaeidae contain pelagic forms of 
flattened shape and great swimming powers, but the structure of the 
mouth-parts in the Corycaeidae points to a semi-parasitic habit. 
Fam. 1. Oncaeidae.—This family, including the genera 
Oncaea, Pachysoma, ete., does not possess the elaborate eyes of 
the next family, nor is the sexual dimorphism so marked. 
Fam. 2. Corycaeidae.—These are distinguished from the 
Oncaeidae, not only by their greater beauty, but also by the 
possession of very elaborate eyes, which are furnished with two 
lenses, one at each end of a fairly long tube. The females of 
Sapphirina are occasionally found in the branchial cavity of 
Salps, and their alimentary canal never contains solid particles, 
but is filled with a fluid substance perhaps derived by suction 
from their prey. S. opalina may occur in large shoals, when the 
wonderful iridescent blue colour of the males makes the water 
sparkle as it were with a sort of diurnal phosphorescence. The 
animal, however, despite the opinion of the older observers, is 
not truly phosphorescent. It may be that the ornamental 
nature of some of the males is correlated with the presence of 
the curious visual organs, which are on the whole better de- 
veloped in the females than in the males. As in so many pelagic 
Copepods, the body and limbs may bear plumed setae of great 
elaboration and beautiful colour, e.g. Copilia vitrea (Fig. 37). 
We now pass on to the rest of the parasitic Copepods,” which 
1 Heller, Reise der Novara, vol. iii., 1868. 
2 For fish-parasites in British waters consult Scott, Fishery Board for Scotland, 
Scientific Investigations, xix., 1900 et seq. 
