ECHINODERMATA 



223 



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 /^;W>' 



"Animate Creation" 

 FIG. 52. A sea urchin, showing spines and extended podia. 



roidea or sea cucumbers. They agree in being without Sea urchins 

 arms or stalk, but their superficial appearance would 

 not suggest any affinity. The sea urchin is variously 

 rounded or oval, conical or flattened, with a hard surface 

 to which are attached numerous spines. These spines 

 may be clubbed, exceedingly large, and thick, or they 

 may be very slender, sharp, and needlelike. There are 

 also very peculiar structures known as pedicellaritz, 

 which may likewise be found on starfishes. They ap- 

 pear to be modified spines, but have the form of a little 

 stem, on the end of which are two or three pincer-like 

 valves, which open and shut. These pedicellanae differ 

 in form and function. Some grasp and destroy minute 

 swimming larvae of animals which might settle on the 



