STAR-FISHES. 



97 



ridges, bearing long, slender diverging spines, some seven 

 or eight in each perpendicular series on each side. 



These spines, when examined with a microscope of high 

 power, present very beautiful objects. We have this in- 

 stant been charmed by the appearance of several of them 

 magnified about two hundred diameters. When the rays 

 of sunlight are reflected from them, they resemble the 

 most elegant taper columns or obelisks, roughened with 

 projecting points shooting perpendicularly upwards, and 

 arranged in parallel rows throughout the whole length; 

 and, as the whole is composed of a substance of brilliant 

 transparency and exquisite polish, the points sparkle in the 

 light as if the whole column were sculptured in crystal. 

 Professor Edward Forbes truly remarks of a spine of this 

 Brittle-star highly magnified, that it exhibits " a structure, 

 the lightness and beauty of which might serve as a model 

 for the spire of a cathedral." 



The internal structure of the spines is no less admirable 

 than their external beauty. The calcareous substance of 

 which they are composed, — a carbonate of lime, mixed 

 with a minute proportion of the phosphate, according to 

 Professor Grant, — which, as we have already observed, re- 

 sembles in appearance crystal or flint-glass, is not solid, 

 but is excavated by a multitude of apparently empty cells, 

 having no connexion with each other, but set in rows and 

 series more or less exact. We notice this because it is the 

 plan upon which all the calcareous parts of the animals of 

 this class are modelled ; the plates of the globular case of 

 the Sea-urchin, those of the Brittle- star, the spines of both, 

 the tubercles of the Cross-fish, the stems and skeletons of 

 the singular Pedicellariw, which we shall presently have 



