SEA-FAN MAKERS. 209 



not reach the whole length of the stalk, but before 

 it reaches either end the point is bound down and 

 bent backwards like a shepherd's crook." 



It has long been known that the sea-pens are phos- 

 phorescent, and, indeed, so much so in one species 

 that it is called the phosphorescent sea-pen (Penna- 

 tula pJiosphorea). Linnaeus has stated that the phos- 

 phorescent sea-pens which cover the ocean bottom 

 cast so strong a light that it is easy 

 to count the fishes and worms which 

 sport around them. Dr. Grant says 

 that " a more singular and beautiful 

 spectacle could scarcely be conceived 

 than that of a deep purple pen, with 

 all its delicate transparent polypi 

 expanded, and emitting their usual 

 brilliant phosphorescent light, sailing FIG . 4I . 



through the still and dark abyss, by POLYPES OF THE 



THORNY SEA-PEN. 



the regular and synchronous pulsa- 

 tions of the minute fringed arms of the whole 

 polypi." In the Scotch seas this species is found in 

 great plenty, sticking to the baits on the fisherman's 

 lines, especially when they make use of mussels to 

 bait their hooks. Professor Edward Forbes con- 

 ducted a series of experiments with these animals, 

 in order to ascertain something of the nature of their 

 phosphorescence, and from these he infers : (i) The 

 polype is phosphorescent only when irritated by 



P 



