REPORT ON THE PENNATULIDA. 201 



escent, and P. pJiosphorea receives its specific name from the fact that 

 it exhibits this phenomenon in an exceptional degree. 



This was well seen in the Oban specimens while living ; the more 

 perfect female specimen when suspended in a jar of sea-water in the 

 dark, and irritated or excited by gently brushing the leaves, exhibited 

 a fine displaj' of phosphorescence, the different polypes when touched 

 showing minute brilliant points of light which appeared to flash over 

 the whole surface of the feather in rapid irregular corruscations. 



Edward Forbes made some interesting observations on the phos- 

 phorescence of Feiuiatula, his main results being as follows: — The 

 pen is phosphorescent only when irritated by touch ; the phosphores- 

 cence appears at the place touched, and proceeds thence in an undulat- 

 ing wave to the extremity of the rachis, but never in the opposite 

 direction ; it is only the parts at and above the point of stimulation 

 that show phosphorescence ; the light is emitted for a longer time from 

 the point of stimulation than from the other luminous parts ; detached 

 portions may show phosphorescence. Forbes also says that " when 

 plunged in fresh water, the Fennatula scatters spai-ks about in all 

 directions — a most beautiful sight ; but when plunged in sjjirit it does 

 not do so, but remains phosphorescent for some time, the light dying 

 gradually away, and, last of all, from the uppermost polypes. One 

 remained phosphorescent for five minutes in spirit."' 



Dr. Wilson,* who, at the request of Forbes, made a direct investiga- 

 tion of the phosphorescent properties of Fennatula, came to the con- 

 clusion that the phosphorescence was not an electrical phenomenon, but 

 was probably due to some " spontaneously inflammable substance." 



The most careful and systematic observations on the phosphorescence 

 of Fennatula are, however, those of Panceri,t who has arrived at several 

 results of great interest. He finds that the light emanates exclusively 

 from the polypes and zooids, and not from all parts of these, but from 

 certain special phosphorescent organs. These " cordoni luminosi " as 

 he calls them are eight longitudinal bands of a fatty substance, 

 situated on the outer wall of the stomach, one band in each of the 

 compartments of the body cavity formed by the mesenteries (Fig. 5, 

 second section) ; and that these phosphorescent oi'gans retain their 

 luminosity after removal from the polype. Panceri states that if any 

 other portion of a polype exhibits phosphorescence it is merely due to the 

 special organs having been broken up, probably by the act of stimulation. 



Panceri finds that phosphorescence may be excited by very various 

 stimuli, mechanical, chemical, thermal, electrical, etc. He finds that 

 if any point in the rachis be stimulated, luminous currents starting 

 from the point of stimulation run both up and down the rachis and 

 along the leaves to their extremities ; and that if a leaf be stimulated the 

 current runs down the leaf to the rachis, then up and down the rachis 

 and along all the other leaves to their extremities. 



♦ Vide Johnston's "British Zoophytes," -iud Ed., 1847, vol. 1., p. 150—155. 

 + Panceri. " Etudes sur la rhosphorescence des Auimaux Marins." Aunales 

 des Sciences Naturelles. Uiucjuicme Series, Touie xvi, 1872, pp. I'i-il. 



