64 SEA-SHORE LIFE 



the original worm breaks up into a number of individuals each pro- 

 vided with eyes and feelers. 



In the Palolo worms f Eunice J of the tropical Atlantic and Pacific 

 oceans, the eggs are contained only in the posterior end of the worm ; 

 and this end is cast off early in the morning of the day of the last 

 quarter of the moon, at the Tortugas, Florida, in July ; and in the Pa- 

 cific in November. This cast off end then swims upon the surface 

 for about an hour, and finally contracts so as to squeeze out all of 

 the eggs after which it sinks to the bottom and dies, leaving the 

 eggs to develop, and the forward etid of the worm to regenerate a 

 new posterior part. 



The Ribbon-Worm, (Meckelia ingens, Fig. 34J, is common in 

 muddy or sandy beaches from South Carolina to Cape Cod where it 

 lives buried beneath the ground near low water line. When fully 

 stretched large individuals are about ten feet long, ])ut when con- 

 tracted even tlie largest are not more than five feet in length. Com- 

 monly the worms are not more than three feet long and about three- 

 quarters of an inch wide, being flat and ribbon-like with bluntly 

 pointed ends, and of yellowish-white color. The body is slimy and 

 the skia is covered with minute cilia wliich wave constantly. These 

 however can be detected only with the microscope. 



This worm is remarkably active and is an excellent burrower, 

 ■forcing its way through the sand with considerable rapidity. It is 

 also a good swimmer, throwing its ribbon-like body into sinuous 

 waving lines as it moves through the water. When distiirbed it 

 rapidly shoots out a long tubular proboscis which arises from a pit 

 on the dorsal side of the head and is not a part of the throat. This 

 proboscis is sometimes thrown out so violently that it breaks off, 

 and then wriggles about very much as if it were a complete worm, 

 while another proboscis is soon regenerated. The proboscis is coa^- 

 ered with an adhesive slime, and serves in the capture of prey ; for 

 this worm feeds upon other worms which it devours entire. The 

 mouth is on the lower side of the head. 



The development of the ribbon-worms or Nemerteans is interest- 

 ing. The larva is helmet-shaped with a broad head region, and 

 covered with cilia which enable it to swim rapidly. After a time 

 parts of the outer skin sink down in four pit-like depressions into 

 the body of the larva and these grow together around the intestine, 



