Phosphorescence of the Sea 521 



Here we have Franklin's final and correct views on the burning 

 of the sea, views that ^vere definitely abreast of the advancing knowl- 

 edge of his time. 



Henry Baker and the History of Noctiluca 



Without a good microscope the previous observers missed the 

 part played by one-celled organisms in phosphorescence of the sea. 

 One of the earliest, if not the earliest reference to the small lumi- 

 nous protozoan, Noctiluca, occurs in Henry Baker's first edition of 

 Employment for the Microscope (1753) , a companion volume to 

 The Microscope Made Easy, the first edition of which appeared in 

 1742. In a chapter entitled, " Of Luminous Water Insects," Baker, 

 after referring to luminous worms on oysters and to a marine Scolo- 

 pendra sent " by a Friend whom I can depend on," stated that he 

 received a letter from Joseph Sparshall describing in sea water little 

 bladders that luminesced. Baker said: 



A curious Enquirer into Nature [Mr. Joseph Sparshall], dwelling at 

 Wells, upon the Coast of Norfolk, affirms, from his own Observations, 

 that the Sparkling of Sea Water is occasioned by Insects. His Answer to 

 a Letter wrote to him on that Subject runs thus: " In the Glass of Sea 

 Water I send with this are some of the Animalcules which cause the 

 Sparkling Light in Sea Water: they may be seen by holding the Phial 

 up against the Light, resembling very small Bladders or Air Bubbles, 

 and are in all Places of it from Top to Bottom, but mostly towards the 

 Top, where they assemble when the Water has stood still some Time, 

 unless they have been killed by keeping them too long in the Phial. 



" Placing one of these Animalcules before a good Microscope; an 

 exceeding minute Worm may be discovered, hanging with its Tail fixed 

 to an opake Spot in a kind of Bladder X (X A Drawing of this came with 

 the Account, but it was too late for the Engraver) , which it has certainly 

 a Power of contracting or distending, and thereby of being suspended at 

 the Surface, or at any Depth it pleases in the including Water." 



The organism seen by Sparshall was undoubtedly Noctiluca, which 

 is easily visible to the naked eye and floats at the surface. The minute 

 worm hanging by its tail to a kind of bladder was the tentacle of 

 this protozoan. It is unfortunate that the drawing arrived too late 

 for publication. Noctiluca was not actually figured until the paper 

 by M. Slabber in 1771. 



Henry Baker (1698-1774), F. R. S., was a well-known micro- 

 scopist, who received the Copley Medal in 1744 and established the 

 Bakerian Lecture of the Royal Society with a giant of one hundred 

 pounds. His books were highly popular and sold well. 



