STARFISHES, URCHINS AND SEA-CUCUMBERS 53 



The mouth is at the centre of the lower side of the disk and is sur- 

 rounded on all sides by the tube-feet. 



In summer and autumn the starfishes are found on rocky- 

 places in shallow water, but in winter they live at greater depths. 



Starfishes feed upon almost any kind of mollusk, but will also 

 devour barnacles, worms, and occasionally sea urchins or even the 

 young of their own species. It is estimated that in 1888 starfishes 

 destroyed $631,500 worth of oysters on the beds of Connecticut 

 alone. Their mode of feeding is interesting. The starfish folds 

 its arms over the clam or oyster, and hundreds of the sucker-like 

 tube-feet fasten themselves to the valves of the shell, so that finally 

 the mollusk yields to the constant pull of the starfish, and the shell 

 gapes open. Then the starfish turns its stomach inside out and 

 engulfs the mollusk. It has been found by expei'iment that a large 

 starfish can exert a steady pull of over two and one-half pounds and 

 that this is sufficient in time to open the valves of a clam or mussel. 



The eggs of the starfish are discharged into the water in great- 

 est abundance during the last three weeks of June, although tliey 

 are also to be found throughout the summer, and occasionally even 

 in winter. These eggs soon develop into little transparent larva? cov- 

 ered with tortuous lines of waving cilia, and provided with long 

 flexible tubercles. They swim slowly about near the surface, and 

 feed upon minute organisms until they grow to be about one-eighth 

 of an inch long. Then the iipper and lower halves of the star be- 

 gin to develop xipon both sides of the stomach, and in a few hours 

 all of the anterior part of the larva and the tul)ercles are absorbed, 

 and only a minute star, about as large as a pin's head, is seen upon 

 the bottom of the ocean. 



Myriads of these little stars settle upon sea weeds and eel grass, 

 and begin at once to devour the young clams which also begin life 

 in the same places. Professor Mead found that one of these little 

 stars devoured over 50 young clams in 6 days. The starfishes grow 

 rapidly, and in one year they may have arms 2^ inches long and be 

 ready to spawn. 



It is certain that the menhaden devour myriads of starfish larvte 

 as they swim through the water. 



Normal starfishes have five arms, but occasionally one is found 



