SEA-CUCUMBERS. 4 ! 



to $600,000. Spines of certain Echini are used as slate-pencils in seme 

 countries. 



FIG. 40. Development of sea-cucumber. A, jelly-like animal swimming ; 

 a, sea-cucumber forming- within. B, later form, showing tentacles 

 and feet. 



Specimens for Study. Living crinoids are not generally 

 obtainable, but the fossil stems are to be found in various 

 localities (see " Geology "). The stomachs of cod and 

 other fishes often yield brittle stars not found near shore. 

 The anchors, dumb-bells, etc., of Holothurians can be seen 

 by treating the skin to a solution of potash, and should be 

 mounted for the microscope. 



Works on EC hinoderms for further reference. 



" Challenger Reports " ; " Depths of the Sea," Sir Wyville Thorn- 

 son ; " Smithsonian Reports " ; Moseley's " Notes of a Naturalist " ; 

 "Natural History of the Star-Fish," A. Agassiz, in "Memoirs of Mu- 

 seum of Comparative Zoology " ; " Echinoderms of New England," 

 A. E. Verrill, in " Boston Journal of Natural History," vol. x ; " In- 

 vertebrata of Vineyard Sound," Verrill ; "Seaside Studies in Natural 

 History," Agassiz ; " Homologies of the Pedicellarise," " American 

 Naturalist," vol. vii, Agassiz ; " Reports of the United States Com- 

 missioner of Fisheries." 



