8 THE ZOOLOGIST. 



light is emitted (in Pelagia), and conveyed to the whole external 

 epithelium. 



Many of the Ctenophores are luminous, and in our own seas 

 Beroe at various stages is one of the most prominent. Their 

 enormous numbers in quiet seas like Bressay Sound and the 

 Firth of Forth make the effects more striking, though the in- 

 tensity of the phosphorescence is less than in the Medusse. The 

 photogenic material is distributed along the gastro-vascular 

 tracts of Beroe. Lesueuria, again, which is met with in multi- 

 tudes in St. Andrews Bay, has a bright bluish (steel-blue) light. 

 Moreover, as Prof. Alex. Agassiz observes, the phosphorescence 

 is equally brilliant in the egg, even in its earliest stages (as in 

 Lampyris). It is only necessary to give the jar a shock, when 

 each egg of Pleurobrachia becomes brilliantly luminous. There 

 can be no special glands (as Panceri describes in other forms) 

 in such a case, but the protoplasm of the egg, as Watase 

 supposes, probably contracts and emits the light. 



The Sea-pens amongst the Alcyonarians are perhaps the 

 best known and most beautifully phosphorescent forms, especi- 

 ally the common species so abundant off the Firth of Forth. 

 Panceri found that the light proceeded from eight white cords ad- 

 hering to the outer surface of the alimentary canal of each polyp, 

 and that the cells of these contained a substance of a fatty nature, 

 the oxidation of which caused the light, and there were also 

 multipolar cells containing albuminous granules. On irritation 

 the light, after a brief interval (four-fifths of a second — Panceri), 

 flashes along the rows of polyps in a somewhat irregular manner. 

 The larger Funiculina and Umbellularia are equally phosphor- 

 escent ; the former, according to Sir Wyville Thomson, is 

 resplendent with a steady pale lilac phosphorescence like the 

 flame of cyanogen, and always sufficiently bright to make every 

 part of a stem caught in the tangles distinctly visible. He 

 mentions also that Umbellularia is so brightly phosphorescent 

 that it is easy to determine the character of the light ; while, 

 with respect to the Corals, Isis and Gorgonia, he conjures up a 

 Gorgonian forest at a depth of six hundred fathoms off the 

 Spanish coast as like an animated corn-field waving gently in 

 the slow tidal current, and glowing with a soft diffused phos- 

 phorescence, scintillating and sparkling on the slightest touch, 



