AI^THOZOA HYDROIDA. 91 



seems to refer more particularly to the phosphorescence of 

 zoophytes. 



" While thus with pleasing wonder you inspect 

 Treasures the vulgar in their scorn reject, 

 See as they float along th' entangled weeds 

 Slowly approach upborne on bladdery heads ; 

 Wait till they land, and you shall then behold 

 The fiery sparks those tangled fronds enfold— 

 Myriads of living points ; th' unaided eye 

 Can but the fire, not the form descry." 



It has been questioned whether this phosphorescent 

 fluid is a secretion of life and health, or the result of some 

 partial decay and decomposition. Dr. Johnston thinks that 

 this has not yet been ascertained,, but seems rather disposed 

 to favour the latter opinion. '^ No species/^ he says, " has 

 been seen luminous in its natal site, and when undisturbed; 

 but after being torn from their attachments, or tossed 

 ashore or trodden upon, or carried away to the home of 

 the experimenter, and variously irritated, then the tiny 

 lamps shine forth momentarily, die away again, and are not 

 relit unless some new shock or injury is given.''^ Prom any 

 experiments that I have made, I would say that the livelier 

 and fresher they were, the more capable they were of lumi- 

 nosity. The Sea-pen is of the Asteroida, but I found it as 



