VIRGULARIA. 197 



and that when roughly touched in the dark^ a transient 

 gleam of light was emitted. A very interesting statement 

 as to this phosphorescence may be found in Dr. Johnston's 

 ' History of British Zoophytes/ from which we shall extract 

 only a little. From experiments made by himself and Pro- 

 fessor E. Forbes, and others, they were led to infer, first, 

 that the polype is phosphorescent only when irritated by 

 touch; secondly, that the phosphorescence appears at the 

 place touched, and proceeds from that to the extremity of 

 the polypiferous portion ; thirdly, that only those parts 

 above the place touched give light ; fourthly, that the light 

 continues longest from the part touched ; fifthly, that sparks 

 of light are sometimes sent out when the animal is pressed, 

 and these were found to arise from ejected spicula. 



Genus XYII. YIRGULARIA, Lamarck. 



Gen. Char. Polype-mass free, linear-elongate, supporting, to- 

 wards the upper extremity, sessile lunate lobes, embracing the 

 stem obhquely, and bearing a row of cells on their margin. — 

 Johnston. 



1. ViRGULARiA MiRABiLis, Sca-rush, Mr. Simmons. (PL 

 XII. fig. 40.) 



