24 SPONGES 



(c) Colour. The colours of sponges are very varied, and often 

 very bright, especially in the case of species inhabiting the shore- 

 line, rendering them very conspicuous objects, and contributing 

 largely to the display of colours in the submarine scenery of caves 



Fio. 38. 



Stylocordyln stipitata, Crtr. 

 (after Agassiz). $. 



Fio. 37. 



Espcriopsi* challengeri, R. (after 



Ridley). J Etispongia officitialis, L. (after Schulze). J. 



and sheltered spots along the coast. Many sponges, however, have 

 no special colouring-matter, and then are simply white or gray, the 

 prevailing tint amongst Calcarea. The littoral species of Demo- 

 spongiae, on the other hand, are usually brightly coloured, especially 

 in the Monaxonida and Keratosa, various shades of yellow, orange, 

 red, or lilac being the prevailing tints, but blue is not uncommon, 



