New-York tribune., 1872-05-07
NEW PUBLICATIONS.
DAMS coRALs AND CORAL ISLANDS. =.

Professor Dana's public sciehuuc eMoV, ~
cenoed with his appointment as minerlos''' ,S ".,
veooqist TO the Wilkes exploring expeolton
Che world from 1888 to lSi2, although the nis' I
If his standard work on mineralogy apPe''oN "a
,.ar previous to his departure on the pro'i'o'e
-, rr,o or,isa was one Of remarkable interest," |
IN every way but especially in the "u.'s " !
,overy with which il enriched the domain oi 'no
rrol sciences Each morning was enllvcheu ny VIC
.i,ht NJ tho strange and curious marine an'in"s
which were gathered by the ships aue' anu ioi"ieo
the study of the day The course Oh 'ne >orso, w''
sften among coral islands with their oeaueiui Nv
ing groves above and within the wateisj or III the
midst of the mountain islands OF the Pacihc, WIN
vo;r eyuberaut forests Of palm and fern In troat
NJ lofty preoipices gayly dTaped with the men
foliage Of the tropics and alive with innamerapie
,aterfaIls; while the burning cones of volcanic
mountains threw q lurid light over scenes OF weird
glamour and epchantment. The romantic features
Of the voyage brought viydly before the reader
h Professor Dana's picturesque descriptions In DIS
preface although they scarcely s1lrpaSs the vlgor
and brilianCy of the narrative in the main body OF
the work Its scientific results are familiar to the
searued world by the admirable monograph on
"Zo0phytes,' first published in an elegant quafto
In 1876. from winch date Professor Dana has
held the rank Of at least, one of the most eminent
authorities on the subject of which 1t treats. 'he
present volume contains the materials collected In
the "Report on Zo6phytes,o which. as only one
hundred copies published by the Governments
has long been out of print but it has been greatly
extended in iis details, and enriched with the addl-
iions made to the science by other students during
The interval of thirty years II now forms thor
sughly exhaustive trease the natural history of
sorals in which the present state OF knowledge Is
exhibited in n method adapted TO popular reading
but without any sacrifice of scientific precision.
Al bnrna hi fha
Of 80 many of our readers that they will doubtless
he Rratifed with brief account of the origin and
nature Of the ornament. which besides enhancing
the charms of beauty plays so conspicuous and wou-
serful part in the formation of certain geological
localities.
The CHEF source of coral is the eecretion of living
organism occupying the lowest part of the scale OF
animal life and which is knewn, i'll modern science,
ander the name Of polyp. Coral is the stony frame
which belongs to these animals. as skeleton be-
longs to an individual of the higher orders of the
NAL kingdom. The process of formation is precisely
nrniar In each case il is a simple animal secretion
IF stony matter from the almelt on which the ami
nal feeds Carbonate of lime, IN each case, s always
sne of the constituents Of the secretion. Coral is
aot the handiwOrk of the polyp, like the honey
somb Of the bee, the hillock of colony of ants
His no more the result Of labor than the production
nf bones in the human frame but each individual
secretion of that portion to which it Is attached.
The common garden aster affords good idea Of a
polyp, both in external form and in decacy of color
ne The aster consists Of a tinted disk bordered
Gith one or more series of petals. The polyp flower
IA its usual form, has a disk fringed around with
petsl-hke organs called tentacles. Below the disk
there is a stout cylindrical pedicel, which contains
the stomach and internal cavity of the polyp. The
mouth which opens into the stomach, is at the cen
l;olr ba aEa cd
BY the secretions Of the polyp is called
sorallum These socretions take place among
the tissues Of the sides and lower part
,f the animals, but in the disk stomach, as
ulls would interfere with the functions of those
organs The bottom of the polyp-cell is often mere
porous mass but in many cases, is quite solid. The
sohdity is often increased, with the age OF the
polyp, by additions to the exterior Of corallum.
In some species tho skin gradually disappears, or
dies away and leaves the cOrallum bare, while all
within is alive in those cases, the skin before dis
appearing often adds a layer Of stony material TO
The exterior giving greater tirmness 10 the whole
The tentacles of the polyp are small, compared
with the size of the animal They scattered over
Che disk, instead of being in regular circles Each
sf the teutacles stands where new ridge Of coral
begins process of budding takes place very similar
10 the budding process IN vegetation. The bud COM
nences as slight prominence on the side of the
trcle of tentacles grows out around it, and continues
10 Increase till the young finally equals the parent in
sze In some species the young does not separate
from the parent, and the budding thus produces a
compound group The process continues, in
pertain instances until hundreds of thousands
aave proceeded from a single germ, forming a
coiony of several feet in breadth or hight.
In all compound groups, the connection of the
polyps is Of the most intimate kind. The several
polyps have separate mouths and tentaces and sep
arate stOmachs, but with these exceptions there is
no individual property. They coaesce by interven-
ng tissues, aud there is a free circulation of
auds through the numerous pores The whole coral
of united pOlyps is like living sheet Of animal
matter, fed and nourished by numerous mouths and
~ MARY stomachs Polyps thus clustered constitute
she greater part Of the Towering display Of coral
reefs.
The large massive forms of stony eorals are due
10 the fact that the combinations of united polyps
life and death going together at the same
time. The condition of growth is favored by the
soral secretions which give the polyp a chance TO
mount 1pwaTd on the coral as it engthens it by
secreons at the top. But at last the polyp deserts
the lower part of the coraum, as growth advances,
which then dies except portion at the extremity
of each branch. The tissues that once filled the
ees Of the rest Of the corallum dry away Instances
are found in which the living part contains a
great number Of pOlyps growing and budding
with all the exuboTance Of vitality. while be-
sow the old polyiis gradually disappear, and even
their cells become superficial aud fade out But this
death not in progress alone the base of the column
Or branch. The whole interior of a coralum is gen
orally dead. while the dead coral below is of rocky
armness- often stronger than ordinary limestone or
marble, serving as an evcr-risng basement for
lha cfin 0tr,.,