CHAPTER VI. 



GEOGRAPHICAL DISTRIBUTION OF ANIMALS. 



If we are to understand animals, we must also consider their 

 habitats. 



(i.) Pelagic Life. — The original cradle of life was probably 

 in the sea, and there a vast number of animals now live. 

 Those which inhabit the open sea near the surface are con- 

 veniently called pelagic. Among these are many Protozoa, 

 e.g., Radiolarians, some Stinging-animals, e.g., the Portu- 

 guese man-of-war {Fhysalia), small Crustaceans, an insect 

 {Halobates), some free - swimming Gastropods, the sea- 

 butterflies or winged - shells (Pteropods), free - swimming 

 Tunicates, e.g., the fire-flame CPyrosomd), many Fishes, e.g., 

 herring and mackerel, besides some Birds, and cetacean 

 Mammals. They often live in shoals, and feed on their 

 neighbours, or on the " sea soup " of Algse. Many are noc- 

 turnal. Most are translucent or brightly coloured, and very 

 active. 



(2.) Littoral Life. — ^From the open sea primitive animals 

 probably passed to the shore. This has been the great 

 school of life. Food is usually abundant, but reproduction 

 is prolific, and thus there is great competition. Wits are 

 sharpened, and the vicissitudes of time and tide have surely 

 been no less influential. " It was in the littoral region," 

 Moseley says, " that all the primary branches of the 

 zoological family tree were formed ; all terrestrial and deep- 

 sea forms have passed through a littoral phase." The 

 shore fauna includes many Protozoa, Sponges, Stinging- 

 animals, such as sea-anemones and zoophytes, " worms " of 

 all sorts. Starfishes, Crustaceans of many kinds, Molluscs, 

 sedentary Ascidians, many Fishes, a lizard {Amblyrhynchus), 



