ANTHOZOA. 57 



have never exhibited any capability of locomotion. Some 

 species, when disturbed, become highly luminous, inso- 

 much, that the statement of Linnaeus, that the "phos- 

 phorescent Sea-pens cover the bottom of the sea, and 

 there cast so strong a light that it is easy to count the 

 fishes and worms sporting among them," is by no means 

 devoid of foundation. 



Hitherto we have seen the solid part either stony 

 or horny, called the skeleton or polypidom, deposited 

 within the living flesh, but there are some species of 

 Anthozoa in which it forms a protecting sheath to 

 the bodies of the Polypes which are lodged in its 

 interior. The elegant aggregation of tubes called 



The Organ-pipe Coral (TuMpora* Musica) is an example of such 

 a structure (Fig. 39). It consists of small cylindrical tubes of a 

 rich crimson hue, placed nearly parallel, but at a short distance 

 apart, and united at regular distances by successive stages of hori- 

 zontal plates, that divide the series into ranges, or stories, like the 



FIG. 39. OUGAN-PIPE CORAL. 



different floors of a house supported by many pillars. From the 

 inouth of each tube, in the living state, protrude the eight tentacles 

 of a starry Polype of a brilliant green colour, forming a striking 

 contrast with the crimson polypidom. 



Actiniae.")' In the succeeding group of Polypes, while 

 the general form and structure of the Anthozoa are pre- 

 served, we find an organization much more complex than 



* Tubus, a tube ; porus, a pore. 

 f aKrlv, aktin, a ray. 



D 3 



