486 



OF ECHINODERMATA. 



tant of our seas, has lately been found in considerable numbers 

 at Torquay (by Mr. Kiugsley), and might probably be met with 



Fig. 241. 



tw\ 



Fig. 242. 



Wheel-like plates from skin of CfUrodota 

 vwlucea. 



Calcareous skeleton of Synapia:—/^. piale imbedded in skin ; b, the same, with its anchor-like spine 

 attached; c, anchor like spine separated. 



more frequently if carefully searched for. Not having had the 

 opportunity of examining a specimen of this animal, the Author 



is unable to say whether or not its 

 integument possesses the very re- 

 markable wheel-like plates, repre- 

 sented in Fig. 242, which are found 

 in the skin of Chirodota violacea, a 

 species inhabiting the Mediterra- 

 nean. These plates are objects of 

 singular beauty and delicacy, being 

 especially remarkable for the very 

 minute notching (scarcely to be 

 discerned in the figures without 

 the aid of a magnifying glass) which is traceable round the inner 

 margin of their "tires." There can be scarcely any reasonable 

 doubt, that evei-y member of this order has some kind of calca- 

 reous skeleton, disposed in a manner conformable to the examples 

 now cited ; and it would be very valuable to determine how far 

 the very marked peculiarities by which they are respectively 

 distinguished, are characteristic of genera and species. The 

 plates may be obtained separately, by the usual method of treat- 

 ing the skin with a solution of potass ; and they should be 

 mounted in Canada balsam. But their position in the skin can 

 only be ascertained by making sections of the integument, both 

 vertical and parallel to its surface; and these sections, when dry, 

 are most advantageously mounted in the same medium, by which 

 their transparency is greatly increased. All the objects of this 

 class are most beautifully displayed by the black-ground illumi- 

 nation (§§ 61, 62) ; and the same method, when applied to very 

 thin sections of Echinus-spines, brings out some effects of mar- 

 vellous beauty. 



320. Echinoderm Larvce. — We have now to notice that most 

 remarkable set of objects, furnished to the Microscopic inquirer 

 by the larval forms of this class, for our present knowledge of 

 which, imperfect as it still is, we are almost entirely indebted to 



