1889] Walks Under the Sea by a Coral Strand. 949 
The comparison of a coral reef to a garden of plants or of the 
branching coral to a tree has a significance which it is interesting 
to notice. The tree and coral agree in being plant and animal 
communities, leading a composite or corporate life of mutual 
benefit. That the tree is a community is seen by its reproducing 
by buds, by cuttings and roots, as in the case of the Banyan or 
Pagoda Fig Tree of India, where a whole forest may arise from a 
single seed. The life of the tree is moreover near the surface, in 
the sap wood, while the heart is practically dead and useless, ex- 
cept for support. 
So the coral starts as a simple egg or cell, and by the asexual 
process of budding builds up a community. The coral stock is 
alive only at the surface, the superficial polyps resting on the dead 
skeletons of previous years, as the living wood rests upon the 
rings of old growth. This comparison fails completely with the 
feeding of these communities, since the tree takes its food not 
only by the leaves but by its new roots, while a coral has no liv- 
ing roots, but gets all its nourishment from the water through the 
mouths of the individual polyps. 
An abraded skin and lacerated fingers await the diver on a 
coral reef, for its wonders cannot be explored without cost. The 
indescribable glimmer which pervades the transparent waters, sub- 
dues and blends all distant objects, and plays in a green light at 
the surface. This is the veil which the sea nymphs hold before the 
eyes of the visitor to their realms. 
A light cream-colored species related to the fan-corals are the 
" nettles" of the reef, which one is sure to meet on his first visit 
thither, and equally sure to avoid on his next. They encrust 
stones or corals of other species, and, being amply provided with 
poison cells, are like fire to the touch. Most of the common corals 
and sponges are found at ebbtide in from one half to two fathoms 
of water or even at less depths. They die quickly when exposed 
to the sun, and if transferred to the sea again they become skele- 
tons in a few hours. 
The black sea urchin {Diadema) to which allusion has been 
"^ade, is the bug-bear of the reefs, and every experienced person 
gives it a wide birth. The white sand is sometimes blackened 
