312 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



definite shape, so that the loss of individuality which occurs later 

 is not the original, but only a coenogenetic peculiarity. The 

 largest Sponge of definite shape and attaining a height of one 

 metre or more is Poterion. 



2. The color. 



In many Sponges the color is less variable than shape and size, 

 even in the indefinitely shaped species it never varies near as much 

 as often in higher animals. I consider the colour in life as a very 

 constant and characteristic feature, so much so, that I would always 

 be inclined to consider a Sponge as belonging to another species ; 

 when the color differs though otherwise similar in shape and 

 structure. Unfortunately the colour is very delicate and always 

 fades in spirits or changes even totally in a few minutes. 



The outer sui-face is mostly monochromatic, although it happens 

 sometimes that one part of a Sponge is lighter than another. 

 &pots or figures of any kind never occur in the surface color. 

 Sponges may have all colors except green. (Spongilla sometimes 

 contains chlorophyll and then appears green.) 



When the colour is not uniform then the lower side is always 

 lighter than the upper, as in fishes. This appears to be less of a 

 protective arrangement than a consecpience of the photographic 

 effect of the light, which causes the exposed surfaces of the 

 Sponge to attain a darker hue than those which are always in 

 shade. If the colour of the Sponge is not uniform then the 

 lighter part is always the same tint as the darker, only a lighter 

 shade. We have here apparently the same difference as between 

 the colours of the soles and palms and the other part of the skin 

 of dark human tribes. Deep sea Sponges are always colorless. 



The Calcareous Sponges are white or light yellow, the Horn- 

 sponges always richly coloured, yellow, orange, blue, red or violet; 

 the Siliceous Sponges, with the exception of those from great 

 depths (Hexactinellidpe and Lithistida?) also appear coloured, but 

 not so intensely as the Ceraospongia?. The interior of the Sponge 

 is mostly of a similar hue as the surface but always more dull. 



