54 SEA-SHORE 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. 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 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 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, (Cribrella sanguinolenta, ig. 26), 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 within rocky tide-pools from the 
eastern end of Long Island to the Arctic Ocean. 
