252 



METAZOAN PHYLA 



289. Behavior. — The behavior of the earthworm has been described. 

 That of other types seems to be similar, subject to the possibihties and 

 Umitations depending upon different modes of Hving and in some cases 

 to hfe in a fixed tube. Many annehds have eyespots or eyes. An 

 eyespot is simply an area on the surface of the body made up of cells 

 with light-absorbing pigment. By the addition of other parts such an 



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ziy'-t^-; 



Fig. 158. — Three types of Gephyrea. A, an echiurid, Echiurus pallasii Guerin, found 

 along the northern Atlantic coasts, of both this continent and Europe, living in sandy and 

 muddy beaches. South in North America to Maine. {From Delage and Herouard, 

 " Traite de Zoologie Concrete.") X ^2- -S, a sipunculid, Dendrostoma alutaceum Grube. 

 Found among coral reefs near shore from Cape Hatteras to the West Indies. (From 

 Gerould, in Proc. U.S. Nat. Mus., vol. 44.) X 4. C, a priapulid, Priapuhis caudatus 

 Lamarck. Found in shallow water along the sand and mud beaches of the Arctic ocean. 

 {From Shipley, "Cambridge Natural History," by the courtesy of The Macmillan Company.) 

 Natural size. 



area becomes an eye. The eye of the sandworm is globular and is com- 

 posed of a cup of pigmented cells, the inner ends of which form rods; a 

 central gelatinous mass, the lens; and a thin cuticular area on the surface, 

 the cornea. The rods, lens, and cornea are all transparent and transmit 

 hght. Some leeches have simple or compound eyes; others which possess 

 no eyes, palpi, or tentacles, are exceedingly sensitive to touch and are 

 apparently attracted to their prey by vibrations coming to them through 

 the water. It is possible that they are also stimulated by secretions from 

 the bodies of the animals on which they feed, also brought through the 

 water. 



