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The Discovery of Plankton 



Top: Scientists aboard ttie Challenger 

 (1872-76) examine plankton 

 specimens in tlie stiip's laboratory. 



Today most of us know the word "plankton," even though we 

 may not be able to give a precise meaning of the word. Like so 

 many current biological terms, it is a comparatively new word, but, 

 more important, knowledge of plankton — those free-floating plants 

 and animals — goes back no further than 1828. In that year, a 

 British Army surgeon and amateur naturalist named J. Vaughan 

 Thompson, who was studying the early stages of crab life, hit on a 

 novel method of catching specimens : He attached a jar to the rear 

 end of a small conical net of fine gauze which he then towed through 

 the water. As water flowed into the mouth of the net and out 

 through its meshes, tiny bits of sea life were caught on the gauze 

 and washed back into the jar. At the end of a run the jar contained 

 a concentration of the microscopic life floating in the surface waters 

 of the sea. 



The invention of the tow net meant that biologists could now 

 catch a form of Hfe that had hitherto escaped them. There is no 

 doubt that the conical net with its built-in jar revolutionized the 

 study of marine biology. Yet Thompson is seldom given credit for 

 his work; a German naturalist, Johannes Miiller, who did not 

 begin to use a tow net until 1844, is generally credited with its 

 invention. Out of Thompson's first use of the net came an inter- 

 esting side discovery: He found that barnacles, which had been 

 classified with the molluscs because of their Umy shells, were, in 

 fact, crustaceans. Their larvae were free-swimming nauplii closely 

 resembling the larvae of crabs. 



An important oflshoot of the use of the tow net was the forma- 

 tion of new concepts in the ecological grouping of marine animals. 

 Most mid-nineteenth-century biologists followed the lead of Ernst 

 Haeckel, a famous German zoologist, by dividing all marine hfe 

 into two groups: the "nekton" (swimming organisms) and the 

 "benthos" (those Uving on the bottom of the sea). Toward the 

 end of the century the word "plankton" was coined to identify a 

 third group (those that drift with the currents). 



The knowledge that the surface waters of the sea contained vast 

 quantities of microscopic organisms — and the realization of their 

 importance in the economy of the sea — did not become apparent 



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