SEA-SIDE STUDIES. 



327 



specimens give us but little idea of this animal. It must be seen and 

 studied while in the sea or in the aquarium, in order to be appreciated. 

 When dead, the suckers which are like those of starfishes and sea- 

 urchins are retracted, and the tentacles are also in a mass, and the 



Fig. 28. Cake-Urchin {Echinarachniua 

 parma, Gray). 



Fig. 29. Key-Hole-TJrchin (Mellita quinqve- 

 *ora, Agassiz). 



whole form is shriveled. But in the water the form is full, and the 

 fringed tentacles are extremely beautiful, and can properly be com- 

 pared to the delicately-branched and beautifully-colored sea-weeds 

 which we all so much admire. 



The " sea-cucumber " has a wonderful power of changing its form. 

 It elongates, contracts, enlarges at each end while it is small in the 

 middle, and thus changes its appearance from time to time. In its 

 power of going to pieces it almost excels the " brittle-star " and the 



& 



fin 



m in 





Fig. 30. Holothurian, or " Sea-Cccumber " {Pentacta fronclom), North Atlantic. 



starfish, Lhidia, already noticed. It breaks off its tentacles, and yields 

 up other parts, at will ; and it has been known, when disturbed, to 

 eject all its internal organs, thus leaving itself only an empty sac ! 



The " sea-cucumber " has no hard parts, excepting the merest cal- 

 careous particles imbedded in the thick, leather-like covering. These 



