10 THE ZOOLOGIST. 



material is formed by the secretory process of the protoplasm, 

 accumulates along the course of the muscle-fibres, and manifests 

 itself in sparks or scintillations in the line of the ventral longi- 

 tudinal muscles. 



In the SyllidcB the widely distributed Eusyllis tubifex, so 

 abundant in transparent tubes on tangle-blades, is one of the 

 most conspicuous examples. Under irritation a fine green light 

 is emitted from the ventral aspect of each foot, and the scintilla- 

 tions seem to issue from many minute points at each area, flash 

 along both sides of the worm posterior to the point of stimulation, 

 and then disappear. Under severe irritation the animal remains 

 luminous behind the injured part for nearly half a minute, while 

 the surface of granular light in each segment is larger than 

 usual, and in some instances the areas of opposite sides are con- 

 nected on the ventral aspect by a few phosphorescent points. 

 The body behind the irritated region has a pale pinkish hue 

 immediately after the emission of light, showing that the 

 luminosity is diffused. In this family the emission of light 

 seems to be due to the same physiological process as in the 

 Polynoidce — no mucus being secreted. 



In the family of the Chcetopteridce, as in the common species 

 in the South of England and the Channel Islands, the phos- 

 phorescence is very beautiful, bright flashes being emitted by 

 the posterior feet. The most vivid luminosity, however, is at a 

 point between the lateral wings of the tenth segment, where a 

 quantity of mucus is secreted, and which can be drawn out as 

 bluish purple fire of great intensity, the light gleaming now and 

 then along the edges of the wing-like processes— at once illumi- 

 nating the surrounding water, and eliciting the admiration of 

 the observer. In all probability, in this case, the oxidation of 

 the secretion by the oxygen in the water suffices for the pro- 

 duction of light. A very characteristic odour similar to that of 

 phosphorus in combustion is given out by the animal during 

 such experiments, and Quoy and Gaimard formerly observed 

 that an odour resembling that around an electric machine is 

 emitted by luminous marine animals. 



Our patient and laborious countryman, Sir John Graham 

 Dalzell, noticed that when irritated Terebella figulus gives out 

 a copious blue refulgence intermingled with a reddish flame. 



