SEA-LILIES, SEA-URCHINS, ETC. 



387 





Individuals which live in deep water, as they obtain not only what they collect 

 by themselves, but they also receive a rain of dead organisms from the upper 

 layers. The size of crinoids accordingly depends upon the amount of their food- 

 supply, so that the largest individuals might be expected to occur in the deepest 

 water. But where streams of ice-cold water, as on the west coast of Greenland, 

 or larger quantities of fresh water at a higher temperature, as on the coasts of 

 Cuba, Guadeloupe, and Japan, flow into the ocean, they prove fatal to minute 

 organisms, and in such situations the increased food-supply renders it possible 

 for crinoids to nourish and attain a large size in comparatively shallow water. 

 In some instances, in- 

 deed, the individuals of 



certain species attain j 



their maximum size in 

 situations of this nature 

 Crinoids present all col- 

 ours except blue, but the 

 smaller stalked forms 

 are invariably yellow. 



Feather-stars, and 

 apparently also fixed 

 crinoids, attain a great 

 development in the 

 Austro-Malay Archipel- 

 ago, the Australian 

 representatives of the 

 former group being 

 specially noticeable for 

 their brilliant and 

 varied colouring. The 

 star - fishes, to which 

 allusion has been made 

 in an earlier chapter, 

 belong, like sea-lilies, to 

 the class Echinodermata, 



and likewise also attain great numerical development as well as extreme 

 brilliance of colouring in the Austro-Malay region. Tropical seas are also 

 favourable to the development of sea-urchins in the matter of size ; the spines 

 of certain species from the Great Barrier Keef of Australia measuring as 

 much as a foot in length. In another section of the same class sea-cucumbers, 

 or holothurians, are in the main a tropical group. These organisms, some 

 of which furnish the trepang, or beche-de-mer, so dear to the palate of the 

 Chinaman, are typically cucumber-shaped or even worm-shaped, echinoderms, 

 with soft, flabby skins, and a ring of tentacles surrounding the terminal mouth. 

 As a well-known species, mention may be made of Hyndmann's sea-cucumber 

 (Cucwmaria hyndmanni) inhabiting the Mediterranean and both Atlantic coasts, 

 at depths ranging down to 60 fathoms. The black sea-cucumber (Holothuria atra), 



HYNDMANW'S SEA-C'UCU.MBER. 



