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 011 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. 



Nicothoe 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 



