1875.] Notices of Books. 535 
and laminated structures, white, yellow, or red, which adorn our 
museums under the name of ‘corals,’ are commonly said to be 
the ‘‘work”’ of certain minute worms, or werse still of ‘‘insects,”’ 
—a term which so applied always sets our teeth onedge. These 
little creatures by their ‘toil’? and ‘skill’ are supposed to 
build up islands from out of the profoundest depths of ocean. 
Each branch of coral is supposed to be “ the constructed hive or 
house of a swarm of polyps, like the comb of the bee or the hil- 
lock of a colony of plants.” The pores are described as cells 
into which the individual ‘‘ insects”’ can retire for shelter or 
concealment. 
All this, and more of a similar tendency, may be read in certain 
popular treatises on natural history, or, for those who prefer verse 
to prose, in Montgomery’s ‘‘ Pelican Island,” concerning which 
our author remarks, with perfect truth, that ‘‘ more error in the 
Same compass could scarcely be found.” In sober reality, the 
polyps elaborate coral, not by skill or toil, but by unconscious 
secretion, just as the bird forms the shell of its egg, or the quad- 
ruped develops its bones. Instead of the coral being a house, 
it is rather a skeleton, having its place within the animal. Polyps 
propagate by a process of ‘‘ budding” as well as by ova, the 
former method being more general among the coral-forming 
species. This accounts for the branch-like structure of the 
corals. 
The notion of polyps building up islands from the bottom of 
deep seas is now known to be mythological. Coral is certainly 
found at great depths, but it is never discovered in a living state 
beyond twenty-five fathoms. Hence, the origin of coral reefs 
was wrapped in mystery until Darwin, during the celebrated sur- 
veying voyage of the Beagle, succeeded in solving the question. 
Coral cannot live below twenty-five fathoms, and yet it is found 
extending downwards to far greater depths, dead in the lower 
regions, but living above. ‘This is only possible on the supposi- 
tion that the foundations upon which the reef was ‘“ built”’ have 
gradually sunk down, whilst the upper part continues to be ex- 
tended, so as to keep its level, or even to rise to a certain height 
above the surface. Hence, these reefs become of the profoundest 
interest to geologists, serving as evidence of ateas of subsidence, 
and, in tropical seas at least, marking the position of islands 
which have long ago disappeared. 
Dr. Dana’s views on the origin and signification of coral-reefs 
coincide in all main points with those of Darwin. The theory 
of our great English naturalist, which the author has studied, not 
in the closet, but among the living objects of which it treats, 
gave him, as he informs us, on his ocean journeys, ‘‘ not only 
light but delight, since facts found their places under it so readily, 
and derived from it so wide a bearing on the earth’s history.” It 
is still more important for us to learn that Darwin’s work on 
‘Coral Reefs’ appeared at a time when the author’s ‘“‘ Report”’ 
WOL.:V. (N:S,) ac¥ 
