266 OCTOBER 



luminous under certain conditions, generally displaying 

 the phenomenon at the moment of irritation ; the light 

 being evolved, not apparently by any proper organs, 

 but either by the whole of the marginal ring, or by the 

 (often coloured) swellings that are seated at the base of 

 the tentacles. 



The following appearances proved the luminosity of 

 this beautiful ^Equorea, on being subjected to experi- 

 ments in the dark. When with my finger-nail I tapped 

 the glass jar in which two specimens were floating at 

 the surface, instantly each became brilliantly visible 

 as a narrow ring of light, the whole marginal canal 

 becoming luminous. On my touching them with the 

 end of a stick, the light became more vivid, and round 

 spots appeared here and there in the ring, of intense 

 lustre and of a greenish-blue tint. These were, I doubt 

 not, the tentacle-bulbs ; and any one of them would be 

 excited to this intensity by my touching that part of 

 the margin with the stick. The luminosity of the ring 

 was not so evanescent as in some species, lasting several 

 seconds, and continuing to be renewed as often as I 

 molested the animal. The two circles of light, two 

 inches or more in diameter, were very beautiful as they 

 moved freely in the water, sinking or rising according 

 as they were touched, now seen in full rotundity, now 

 shrinking to an oval, or to a line, as either turned side- 



