PORIFERA OF THE L.M.B.C. DISTRICT. 231 



graphic action than the lower side which is always in 

 shade." I therefore merely apply what Lendenfeld said 

 in regard to different parts of the same specimen to dif- 

 ferent specimens of the same species. 



I will not omit to state that in neither of the two cases 

 could one think of accomiting for the colouring by protec- 

 tive resemblance to the environment. The lighter speci- 

 mens especially were as different in colour from the rocks 

 (carbonate of lime at Puffin Island and slate of Ordovician 

 age at Brada Head, Port Erin) as they possibly could be. 

 Altogether it has not been proved yet that sponges ever 

 imitate their surroundings in colour. Out of the numer- 

 ous species of our district which I have had occasion to 

 examine in the living condition, not a single instance 

 seemed to give a sure proof of such an imitation. If here or 

 there a species of sponges, organisms which in their shades 

 and tints show almost as innumerable transitions as the 

 spectrum itself, happens to resemble its surroundings, 

 whilst the vast majority of the other species do not, then 

 it is surely out of place to take that one example as a proof 

 of imitation of the environment. I may quote what Len- 

 denfeld * says in regard to the Ceratosa — "The horny 

 sponges never imitate their surromidings in colour, although 

 some of them, particularly those which have an arenaceous 

 cortex, are very similar in colour to the sea bottom on which 

 they, grow. Most of the horny sponges are, like many of 

 the other shallow water Silicea, very intensely coloured, and 

 it would appear that these vivid colours have been adopted 

 by the sponges for the purpose of frightening their 

 enemies." This seems really to be the only explanation 

 for most of the colours in sponges. Animals which, like 

 the great majority of sponges, are so extraordinarily well 

 defended by their skeleton, are scarcely in need of a pro- 



* R. V. Lendenfeld, "A Monogi-apli of the Horny Sponges," p. 742. 



