50 KEPORT ON THE PENNATULIDA. 



The most careful and systematic observations on the phosphorescence 

 of PennaUila are, however, those of Panceri,* 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 baud in each of the 

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

 second section) ; and that these phosphorescent organs retain their 

 luminosity after renaoval 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 phosphorescen<;e 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 both up and down the 

 rachis and along all the other leaves to their extremities. 



A further point of interest determined by Panceri is, that there is 

 always a distinct interval between the application of the stimulus 

 and the first appearance of phosphorescence, and that this latent 

 period has a very constant duration of 4-.5ths of a second. 



It will be seen that these " phosphorescent organs " of Panceri are 

 the same things as the " hepatic cells " of Gosse, which have been 

 described above both in Peiuiatuld and Fiaiicitlhui. t 



8. — Geographical DUtrihution. — 



Fennatula plwsphorea is apparently a common species at various 

 places round the British shores : Ellis says that " great numbers have 

 been taken on the coast of Scotland, especially near Aberdeen : "' 

 Dr. Gray mentions the coast of England and the Hebrides ; and 

 Kolliker gives as localities, besides the coast of England and Scotland, 

 the Mediterranean, especially Naples and the Adriatic, the coast of 

 France, and the Kattegat; to which Sars adds the whole coast of 

 Norway, from Frederickshald to Christiansund. 



* Panceri. " Etudes sur la Phosphorescence des Auimaux Marius." Annales 

 des Sciences Naturelles. Ciuquieme Series, Tome xvi, 1872, pp. 13-21. 



t Hupra. pp. 17 and 42. 



