122 



THE OCEAN WORLD. 



membrane is irritable and encloses the polyp ; 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 vertebrated animals. 

 It has recently been asserted that the tissues of these corals 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 give 

 it a stony consistence. This outer covering developes itself in con- 

 centric beds, between 

 the portion of the axis 

 previously formed and 

 the internal surface of 

 the sclerotic covering. 



The mode of growth in 

 this axis presents great 

 variations. Sometimes it 

 remains simple and rises 

 like a slender rod, some- 

 times it has numerous 

 branches. It is arbores- 

 cent when the branches 

 and their accompaniments 

 take different directions 

 so as to constitute tufts. 

 It is panicked when 

 they arrange themselves 

 on both sides of the stem 

 or principal branches, 

 after the manner of the 

 barbs of a feather. It 

 is fldbelliform when the 

 branches rise irregularly 

 under the same plane ; reticulated, when branches are so disposed as to 

 be attached to each other by network in place of remaining free. 



The Gorgoniadse are found in every sea, and always at considerable 

 depths. They are larger and more numerous between the Tropics 



Fig. 43. Fan Gorgon, magnified. 



