MICROSCOPIC OBJECTS. 56 



Fig. Ill . Spines of a Starfish (Ophiocoma rosula) , x 20. 



Skeletons of any of our Starfishes may be prepared in the 

 same manner as the spines of this species have been treated 

 that is, by soaking in very dilute potassa fusa until the bony 

 structure is cleaned ; but if the fluid is made too strong, the 

 skeleton separates and becomes useless. If the spines only 

 are wanted, the alkali may be used much stronger. Although 

 common, even the ordinary Starfish (Asterias rubens) is wor- 

 thy of microscopical examination. Mixed with the spines 

 are a number of peculiarly shaped bodies called pedicellarise. 

 These are supposed to be the organs of locomotion. 



The spines, pedicellarise, &c. are generally best mounted 

 dry. 



Fig. .112. Spines of Spatangus, x 20. 



These spines, drawn as seen under the parabolic reflector, 

 are taken from the Spatangus, a genus of Echinidse, belonging 

 to the Class Echinodermata, which comprises the Starfishes 

 &c. They show best when mounted in balsam and seen under 

 a low power, although they may be mounted in a dry opaque 

 cell and viewed under condensed reflected light. 



