EEYIEWS. 
295 
theory of the figure of the earth’s solid crust, and the physical connection 
between the tetrahedral figure and a molten spheroidal mass on which is 
forming a solid crust, and the partial deviation of the form of land to a pre- 
sumed macling of the crystal, or a plane of lateral shift between the northern 
and southern hemispheres parallel to the plane of the ecliptic. The further 
explanation of these and other hypothetical views must, we think, await the 
publication of the second and third parts, when the author may endeavour 
to connect more in detail the earth’s surface features with volcanic action 
and the tetrahedral collapse and shift of a thin crust upon the molten 
spheroidal nucleus. 
CORALS AND CORAL-ISLANDS.* 
P ROFESSOR DANA has not taken the same length of time as Mr. 
Darwin in bringing his fine treatise to a second edition. Whereas 
the latter required more than thirty years, his American fellow-worker 
has taken but two in arriving at the second issue of his work. It is satis- 
factory to see that this work is in no way whatever controversial. Though 
we fancied when first we took it up that we should find considerable 
depreciation of Mr. Darwin in its pages, yet really nothing of the kind 
is to be found. It is true that on some points the author holds a view 
which differs from that held by the author of the u Origin of Species.” 
But in every instance that he has to speak of Mr. Darwin, Professor Dana 
uses language which must gratify his opponent extremely, for, though not 
much later than our English savant in the field of exploration, he yet gives 
him the most extreme credit for the value of his labours. 
The book does not require a lengthy notice, because of the fact that the 
present edition coming out so soon after its predecessor has not much in the 
shape of novel matter to offer its readers. Still we may in a general way sketch 
its contents. It first deals with polyps properly so called, which the author 
divides into three groups, and then treats of as living and dead agents. Next 
come the Hydroids, which we should hardly have expected in a work like the 
present. After them come two groups which we certainly think ought not 
to have been described in a book on corals, viz. the Bryozoans, which are, as 
of course the author admits, genuine mollusks — and the Algae or nullipores 
and corallines. Lastly, the true coralline polyps — those which form such 
gigantic masses, or lagoons, on both sides of the equator, at about the 
latitude of 28°. Within this latitude the water ranges in temperature from 
78° to 68°, being in some cases as much as 85° in the Pacific and 83° in the 
Atlantic, and descending in some rare instances, and for a limited amount 
of time, as low as 68°. Under this head of classification the author 
includes some twelve groups of corals, of which seven are inhabitants of 
the hotter and five of the colder climates. Then with a considerable 
* u Corals and Coral-islands.” By James D. Dana, LL.D., Professor of 
Geology in Yale College, &c. &c. London : Sampson Low, Marston & 
Searle. 1875. 
