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 



FIG. 38. 



Stylocordyla stipitata, Crtr. 

 (after Agassiz). 3. 



Esperiopsis cha.llengeri, R. (after 

 Ridley). J. 



Fio. 39. 

 Euspongia officinalis, L. (after Schulze). 



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, 



