572 History of Luminescence 



on sea pens involved experimentation. They were presented in the 

 same paper, Sopra Diverse Produzioni Marine (1784) , in which he 

 reported luminous worms at Portovenere near Genoa. He deter- 

 mined that only the feather part, not the stem of the sea pen lumi- 

 nesced, and found that when the feather part was pressed with the 

 hand a luminous liquid gushed out of a hole in the stem, appearing 

 like a bright fountain in the dark. He appears to have been the 

 first to observe the waves of light which pass from polyp to polyp on 

 stimulation, and are caused by nerve transmission of impulses. After 

 indicating that the light came from the polyps whose shining was so 

 bright at night that candlelight had little effect on it, Spallanzani 

 wrote: ^^ "If one touches the borders of the feather part, the light 

 flows rapidly from the polyps toward the middle of it. In my book 

 I shall spend some time in describing this phenomenon. . . ." This 

 future study never appeared. The " waves of light " were also seen 

 by H. D, de Blainville (1834) , and others, but a comprehensive 

 physiological analysis of their transmission in sea pens had to await 

 the experiments of Paolo Panceri in 1873. He also investigated the 

 histology. 



An early study of stimulation of luminescence of sea pens was 

 made by Edward Forbes (1815-1854) , and published as a letter by 

 G. Johnson in A History of British Zoophytes (1st ed., 1838; 2nd 

 ed., 1847, pp. 150-155) . Forbes drew the following conclusions from 

 his study of Pennatula phosphorea: 



1st, The polype is phosphorescent only when irritated by touch; 2d, 

 The phosphorescence appears at the place touched, whether it be the 

 stalk or the polypiferous part, and proceeds from thence in an undu- 

 lating wave to the extremity of the polypiferous portion, and never in 

 the other direction; 3d, If the centre of the polypiferous portion be 

 touched, only those polyps above the touched part give out light; and if 

 the extreme polypiferous pinna be touched, it alone of the whole animal 

 exhibits the phenomenon of phosphorescence; 4th, The light is emitted 

 for a longer time from the point of injury or pressure than from the 

 other luminous parts; 5th, Sparks of light are sometimes sent out by 

 the animals when pressed— these are found to arise from luminous matter 

 investing ejected spicula. 



Forbes even persuaded his friend, George Wilson (1818-1859) , 

 the distinguished chemist, to determine whether Pennatula evolved 

 electricity like an influence machine or a voltaic battery. By insulat 

 ing the Pennatula in the air or in turpentine and bringing it near a 

 gold leaf electroscope or connecting it to a sensitive galvanometer, 

 no indications of electric charge or current were obtained. Wilson 



'^ Translated by Dr. Luigi Crocco of the Forrestal Laboratories, Princeton University. 



