54 



SEA-SHORE LIFE 



having more or less than tliis number. Some of these variations 

 are the result of accident, but others are congenital. 



Starfishes regenerate readily, and although a single detached 

 arm will not regenerate a new star, it will do so if it be torn off to- 



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Fig. 26; BLOOD-STAR. Massachusetts Bay, Tide Pools. 



gether with about one- fifth of the central disk. Also the central 

 disk if deprived of all of the arms will soon regenerate them. 

 When an arm is injured it is iisually cast off voluntarily very near 

 to the central disk, and regeneration begins at this point. Regen- 

 eration from the injured tip of an arm is very rare. 



By means of their hiuidreds of sucker feet starfishes are 

 enabled to glide rapidly over the softest mud. They can also 

 climb readily and if turned over will quickly right themselves. 

 When the water is perfectly flat and calm they can even move 

 sucker-side uppermost along the surface of the water. 



The Blood Starfish, fCribrella sanguinolenta, Fig. 26 J, is smaller 

 than the common starfish, and its arms are rarely more than an inch 

 long. It is pink or reddish and the arms are almost smooth, be- 

 ing covered with numerous little warts. The leathery skin is quite 

 soft and flexible, and the arms are rounded in cross sections, and 

 taper to a point. 



The eggs are not cast out into the water, but are held around 

 the mouth of the mother until they have developed into little star- 

 fishes. This creature is abundant witliin rocky tide-pools from the 

 eastern end of Long Island to the Arctic Ocean. 



