54 



SEA-SHOKE LIFE 



having more or less than this 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- 



Fig. 26: BLOOD-STAR. .\r:issacliusetts Ba.T, Tide Pools. 



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

 disk if depri\-ed of all of the arms will soon regenerate them. 

 When an arm is injured it is usually 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 hundreds of sucker feet starfishes are 

 enabled t(j glide rapidly over the softest mud. They can also 

 climb readily and if turned over will quickly right tliemselves. 

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

 sucker-side uppermost along the surface of the water. 



Tlie Blood Starfish, fCribrella sangainolenta, Fvj. S6J, is smaller 

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

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

 ing co\ered 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 tlie mother until they have developed into little star- 

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

 eastern end of Long Island to the Arctic Ocean. 



