522 PENNATULA. ASTEROID POLYPES. 



often deeply coloured ; being, in the British species Pennatula 

 phosphorea, purplish-red along the stalk, and orange at its 

 extremities. It is not often that the Pennatulae rise to the 

 surface. They are usually brought up from considerable depths 

 by fishing-lines ; and the fishermen believe that they are gene- 

 rally fixed in the bottom, with their ends immersed in the mud. 

 Some of the Pennatula are very brilliantly phosphorescent ; and 

 the appearance of the larger species, when displaying their 

 luminosity in the dark ocean, is very striking. The disengage- 

 ment of light is, however, by no means constant ; but, as in all 

 other instances of phosphorescence, depends upon the condition 

 of the animal. "When it is irritated or alarmed, a vivid emission 

 takes place ; but this soon dies away. When frequently struck 

 by the waves, it is possible that they may continue the display 

 with little interruption ; but observation proves that, when 

 preserved in calm water, they do not voluntarily disengage light, 



although they readily show it if disturbed. The accompanying 

 figure represents a genus of Alcyonian Polypes, nearly allied to 

 the Pennatula. 



1094. The next group of Asteroid Polypes includes many 

 well-known species, such as the Red Coral, the Gorgonia or 

 Sea-fan, the Antipathes or Black Coral. In all of them the 

 structure of the Polypes is nearly the same ; and the differences 

 of the polypidom chiefly relate to the portion, in which the 

 solidification of the structure has taken place to the greatest 

 extent. It will be recollected that, in the true Alcyonia, the 

 calcareous or siliceous spicula are deposited, as in the Sponges, 

 through the whole mass ; and that, with the exception of the 

 fibrous bands which interlace between the canals, no one portion 



