THE SHORES OF BRITAIN. 67 
strewed every where around. The beauty and no- 
velty of such a scene in the animal kingdom long 
arrested my attention; but after twenty-five minutes 
of constant observation, I was obliged to withdraw 
my eye from fatigue, without having seen the tor- 
rent for one instant change its: direction, or diminish 
in the slightest degree the rapidity of its course. I 
continued to watch the same orifice, at short inter- 
vals, for five hours, sometimes observing it for a 
quarter of an hour ata time; but still the stream 
rolled on with a constant and equal velocity.” 
Sponges, in general, appear ¢o have little choice 
of situation, but to grow wherever the young offset 
or gemmule happens to drop, whether on the rock, 
on a shell, or on asea-weed. If two of the same 
species, growing side by side, come into contact, 
their edges unite, and the two form one mass, so 
perfectly one that the most practised eye could de- 
tect no indication of the line of union. On the con- 
trary, if the neighbours be of different species, the 
edges adhere by contact, but there is no union; and 
both of the contiguous edges will grow up far be- 
yond their natural level, like walls striving to over- 
top each other, until the action of the waves pre- 
vents the continuance of a mode of growth so un- 
natural. Dr. Johnston speaks of two species of 
Sponge which had become so intermingled in 
growth, without being united, that, being of differ- 
ent colours, they presented the appearance of a 
coloured map. The same writer has figured a much- 
branched species (Halichondria oculata), growing on 
the back of a small crab: the latter has a grotesque 
