The Blue Gyancea. 155 



Since the publication of these observations, I have had 

 additional proof of the non-earthy character of the prisms ; for 

 having mounted some, carefully cleansed, on several glass slides, 

 and covered them with plates of thin glass, for future micros- 

 copic observation, I found, after some months, that they had 

 wholly disappeared, leaving scarcely a trace of their existence, 

 though exposed only to the atmosphere, and this admitted only 

 under the edges of the plates of glass. If they had been earthy 

 crystals, it is manifest that they would have remained unchanged 

 both by the atmosphere and by potass. 



The specimen whose portrait accompanies this little memoir 

 lived for two or three days only, in a glass vase of sea- water. 

 Generally I have not been able to preserve these forms in health 

 for a longer period ; though a fine specimen of Ghrysaora 

 cyclonota, whose history I have given elsewhere,* lived under 

 similar circumstances about three weeks. A very gorgeous 

 object was the Gyancea in captivity. The whole umbrella was 

 of a fine rich blue, possessing a sapphirine brilliance and trans- 

 parency, especially when the slanting rays of the setting sun 

 shone horizontally through the mass, as it floated in its glass 

 prison on our drawing-room table. This hue was deepest where 

 the substance of the disk was thickest, while at the surface and 

 edges it melted off into colourlessness. Yet the lower integu- 

 ment or sub-umbrella, being of a far deeper colour, the form of 

 the inner dome, viewed horizontally, was quite broadly defined 

 from the hue of the mass, and seemed like a solid hemisphere 

 of glass within the mitre, of a blue so intense that the sun's 

 rays could scarcely struggle through it. In this the vault-like 

 clefts were fashioned, reminding us of those beautiful paper- 

 weights, in which some exquisitely folded pattern is seen within 

 a perisphere of smooth clear glass. 



It was interesting to observe that by lamplight the hue was 

 very different. As I have often noticed that flowers which by 

 daylight are almost purely blue, show by candlelight a pro- 

 minent red element, before unrecognized, so this fine Medusa 

 became of a fine imperial purple. I suppose the explanation is, 

 that the blue ray is more weakly perceptible by artificial light, 

 and is, therefore, overpowered by the red ray, though this may 

 exist in the compound tint in actually a less ratio. 



I could not detect any stinging property in the tentacles 

 when touched by the hand. Its congener, G. ca/pillata, is de- 

 scribed as so formidable as to be the terror of bathers ; and 

 Edward Forbes has given us a graphic description of an. unfor- 

 tunate swimmer writhing, terrified and tortured, in the clinging 

 grasp of its slimy threads. Much may depend on the varying 

 susceptibility of the human skin to the poison in different per- 



* Devonshire Coast, p. 3G3, el seq. 



