274 



PHYLUM ECHINODERMATA. 



and the following years, and indirectly to the despatch of the 

 Challenger expedition in 1872. 



FIG. 189. Developmental stages of Antedon, much enlarged (from Claus, after W. Thomson). 

 a Free-swimming larva, with tufts and rings of cilia Wr, and with rudimentary calcareous 

 plates. 6 Attached cystid stage of the same animal. O orals, R radials, B basals, 

 Cd centro-dorsal plate, c older stage described as Pentacrinus europaeus with arms and 

 cirri. 



The general form of the body and skeletal plates of Crinoids 

 may be considered under three heads : (1) the calyx and its 

 cover, (2) the arms, and (3) the stem. 



