250 MARINE INVERTEBRATES 
crustaceans, the baleen straining them from the water. Although 
devoured in such immense quantities, and sometimes lying dead in 
sheets of scum on the surface of the water, they maintain their 
numbers by the exceeding rapidity with which they reproduce. 
It has been computed that the descendants of one Cyclops may 
number in one year 4,500,000,000, provided all the young reach 
maturity and produce a full number of offspring. 
One of the free marine forms, Sapphirina, is of especial inter- 
est, as it surpasses all animals in phosphorescence and sparkles 
by day as well as by night. It is one quarter of an inch long, 
and is broad and flat. 
Besides the myriads of free-swimming copepods, there are para- 
sitic forms in great number. The marine parasitic forms are 
commonly known as fish-lice. They have various habits, some 
living as commensals, others attaching themselves to animals 
only to be carried about; the true parasites live upon the blood 
and tissues of their hosts, and may fasten themselves to the exter- 
nal parts of the body or to the internal organs. Whales, fishes 
of all kinds, mollusks, starfishes, jellyfishes, and corals, all have 
some form of parasite, and many have several different kinds of 
guests. It is said that the haddock has more than a dozen which 
infest its external and internal membranes. 
Nicothoé is found on the gills of lobsters. The truly parasitic 
forms are usually very degenerate and lose the characteristics of 
their order. 
ORDER CIRRIPEDIA 
C‘ Curled feet") 
THE BARNACLES 
Barnacles of the genus Balanus (acorn-shells) (Plate LIX) 
are familiar objects on rocky shores, which they often whiten with 
their shells, and those of the genus Lepas are also widely known. 
The name of the order is descriptive of their curled appendages. 
The appendages are fringed like feathers and are drawn into or 
protruded from the shell at will. When extended they are con- 
stantly in motion, and create currents which carry food to the 
