136 



BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



tion by the echinodeniis of the sessile habit; mid the assumption of the sessile 

 habit went hiiiul in hand with the modification of the skeleton in the direction of 

 the tj^je common to similarly inactive forms, such as sponges and alcyonarians. 



Fio. 83.— Lateral view or a specimen or Eudiocrinvs junceus from the Lesser Sunda Islands, showdjo the 



RELATIVE proportions OF THE ARMS, PINNULES, CENTRODORSAl, AND CIRRI. 



Thus, as we understand it, the echinoderra skeleton considered strictly as the 

 echinoderm skeleton was from the first a skeleton of the spicular t_vpe, the counter- 

 part of the skeleton of certain sponges and alcyonarians; but in reality this spicular 

 echinodermal skeleton is not an original dcvolopmont like the spicular skeleton of 



