PORIFERA OF THE L.M.B.C. DISTRICT. ASL 
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 accounting for the colouring by protec- 
tive resemblance to the environment. The lghter 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 animitation. 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 surroundings 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 Monograph of the Horny Sponges,” p. 742. 
