124 
THE OCEAN WORLD. 
membrane is irritable and encloses tlie polype ; it becomes friable or 
arenaceous in drying. The second substance, internal and central 
sustains the first, and is called the axis. This axis presents a horny 
appearance, and was formerly believed to possess chemical characters 
analogous to the horns and hoofs of some of the vertebra ted animals- 
It has recently been asserted that the tissues of those polypiers consist 
essentially of a particular substance which resembles horn, but which 
is called Corneine. A little carbonate of lime is sometimes found 
united with this substance, but never in a sufficient quantity to gi ve 
it a stony consistence. This outer covering developes itself in con- 
centric beds, between 
the portion of the a£ lS 
previously formed and 
the internal surface 
the sclerotic covering. 
The mode of growth i® 
this axis presents grea 1 
variations. Sometimes i* 
remains simple and ris<- 3 
like a slender rod, som e ' 
times it has numerous 
branches. It is arbor W 
cent when the branches 
and their accompaniment 
take different direction 3 
so as to constitute tufts- 
It is panicled wbeu 
they arrange themselves 
on both sides of the stem 
or principal branches, 
after the manner of th® 
barbs of a feather. ^ 
is flabelliform when the 
Fig. 43. Fan Gorgon, magnified. . . . . , l,r 
branches nse irregular^ 
under the same plane ; reticulated when branches are so disposed as to 
be attached to each other by net-work in place of remaining free. 
The Gorgonidm are found in every sea, and always at considerable 
depths. They are larger and more numerous between the Trope- 
