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nearest the stem on the lowest branchlets, become sparklingly 
luminous one after the other, and, when they are all illuminated, 
those of the next branchlets begin to shine, until in succession 
the whole are glowing. A slight interval of time, amounting 
to a second, occurs between the stimulation and the appearance 
of the light, and the Sea-pen 6^- inches long was illuminated in 
seconds. 
On pinching the top of a Sea-pen of this species, the lighting 
up commenced in the nearest polypes, and then those of the 
next lowest branchlets took up the effect, and the phenomena 
of the previous experiment, were simply reversed. 
Again, on irritating one of the polypes at the end of a 
branchlet, its luminosity went to its neighbour, and then all 
followed one after the other ; and if those at the beginning and 
ending of a branchlet were touched, the lighting up was towards 
those in and between them. 
This successional illumination is very decided, and, when it 
is completed, the light is pretty constant. But it is evident 
that on irritating one of the polypes it “ takes fire,” as it were, 
at the edge of the tentacular apparatus, some luminosity re- 
maining on the implement and in the intermediate water. 
These remarks, the results of Panceri’s interesting studies, 
may recall to mind the early experiment of Spallanzani, who, 
on compressing the stem of a Pennatula , obtained a light from 
the other extremity, and the fact that crushing the stem and a 
few branchlets, produces a substance which becomes diffused 
and lights up everything to which it adheres. 
Careful observation has determined that when the pen is 
perfect, the light is emitted from the eight opaque cords of 
each polype, and that it can commence and continue without 
their rupture. On the other hand, rupture of a cord excites the 
luminosity of the whole, and the escaping fatty matter is 
luminous after its separation and after the death of the animal. 
There is no sensible increase of temperature, and the tint of 
the monochromatic light is azure or greenish, but never red. 
In this beautiful instance of this remarkable vital luminousness 
there is evidently a photogenic structure and an elaborated 
organic material capable of producing light after removal from 
the animal. The sequence of illuminating is slow in the whole 
pen, and only at the rate of a yard in 20 seconds — a rate far less 
than that of the movement of nerve force. Yet the presence of 
the lowly-organised nervous element indicates that the regulating 
of the light may relate to it as its function. Clearly the phosphor- 
esence of the Pennatulid is in advance of that of the simpler 
protoplasmic movement of the Protozoa and of the slime of the 
Actinoid. Sir Wyville Thomson notices the coming up, in a trawl 
let down to a depth of 2,125 fathoms of a magnificent u clustered 
