ANTHOZOA ASTEROIDA. 155 



that some of them, or compounds of them with nitrogen and 

 oxygen, should prove spontaneously inflammable. We require, 

 however, not only a combustible, but likewise a supporter of 

 combustion. I would suggest it as a subject well worth the 

 attention of observers, to notice whether or not any bells or 

 bubbles of gas shew themselves around the phosphorescing 

 points of the Pennatula. It is possible that it may secrete 

 air or oxygen along with the inflammable substance. 



" The persistent luminosity of detached points is not against 

 such an idea, for the combustion is ex hypothesi an extremely 

 slow one, and the oxygen of the air secreted along with the 

 combustible may suffice for its support for a long time. It is 

 not necessary, perhaps, to assume a power of secreting oxygen. 

 Air must be constantly separating from its state of solution in 

 sea- water, and attaching itself to the Pennatula, and may suf- 

 fice for maintaining the combustibility of its little lamps. I 

 watched the Pennatulse whilst phosphorescing with micro- 

 scopes of considerable power, but could not detect any air-bub- 

 bles. I am quite unskilled, however, in the use of the micro- 

 scope, and would suggest to those who are experienced in its 

 use, the desirableness of repeating my observations on this 

 point." 



24, Brown Square, Edinburgh, 

 "Dec. 17th, 1845." 



Fig. 34. 



OVA OF THE UOKGONIA. 



