CHAPTER 1 

 Introduction 



Until recently, the use of the word 'plankton' — a term of scientific 

 'shorthand' — was confnied to the speciahsts' jargon, but with the greatly 

 increased spread of knowledge it has gradually crept out until it is now a 

 recognized term for what was previously called 'feed' by the fisherman, 

 and often just 'life' by the layman. It is not so many years since the word 

 did not exist at all; it was coined by Hensen (Fig. i), a German, in 1887 and 

 more critically defined by another German, Haeckel, in 1890. In brief, it is 

 a comprehensive term to include all those living things, plant and animal, 

 that are drifted about by the water movements. It is a most expressive term 

 derived from the Greek TrXavKrov, i.e. that which is passively drifting or 

 wandering. Its constituents range in size from the minute plants that are 

 about 1/10,000 inch to the largest jellyfish which may be a yard or so across. 

 Many of the animals can, of course, swim, but their movements are small 

 compared with those of the water itself. Although they can move up and 

 down through appreciable and often great distances, their general distribu- 

 tion, both locally and geographically, is determined by their environment. 

 By this definition plankton includes also the young free-living stages of 

 many animals which are relatively sedentary as adults, such as the moUuscs 

 and barnacles, the young stages of bottom-dwelling animals such as crabs and 

 worms, the floating hsh eggs and the young fish after they hatch and before 

 their own swimming powers are sufficiently developed for them to choose 

 their own whereabouts. 



Plankton thus takes its place wdth the two other main aquatic com- 

 munities, the 'benthos' living on the bottom, and the 'nekton' which 

 swims about freely. 



There is plankton in fresh water as well as in the sea and the term is no 

 longer confined to its original aquatic field; 'aerial plankton' is sometimes 

 used in referring to insects, seeds and spores windblown from place to place, 

 out of control, as it were, as distinct from deliberate migrations. 



The existence of marine plankton has been known in a vague way 

 almost since time immemorial, but its detailed study is one of the more 

 recent scientific disciplines, and is barely more than 100 years old. In 1845 

 a German, Johannes Miillcr, towed a conical net of fmc-mcshed cloth behind 

 a boat and so became the first research worker on plankton. His catch 

 revealed an entirely new sphere for biological investigation, and it is small 



