232 FOUNDERS OF OCEANOGRAPHY 



planktonic forms are such as remain free and pelagic during 

 the whole of their life (Diatoms, Copepoda, etc.), and Mero- 

 planktonic those that are transitory only, such as the embry- 

 onic, larval and other free stages of benthonic animals 

 (Coelenterates, Echinoderms, Molluscs and many others). 

 Fig. 2, on Plate XVII, shows the appearance under the 

 microscope of a sample of mixed plankton containing both 

 plants and animals, both holo- and mero-planktonic. 



The importance of the plankton in the scheme of nature 

 and in relation to the nutrition of the larger animals of the 

 benthos and the nektonic fishes can scarcely be overstated, 

 and many investigators all over the world — on special 

 expeditions and at biological stations — during the last half- 

 century, have made contributions to knowledge of the nature 

 of the plankton and its detailed distribution both in space 

 and time and the many other problems of its occurrence. 

 Fig. 1, on Plate XVII, shows the plankton net outfit on a 

 Yacht engaged in scientific work. 



The earlier investigations of the plankton were almost 

 entirely qualitative, that is, they consisted in identifying the 

 organisms caught, working out their minute structure and 

 tracing their life-history ; but more recently much attention 

 has been directed to the quantitative distribution of organ- 

 isms in the sea mainly as the result of the elaborate investiga- 

 tions of the Kiel school of Planktologists and the German 

 Plankton Expedition of the " National," through the Atlan- 

 tic, in 1889. Previously, the plankton had been caught by 

 various forms of tow-nets, from the simple open cheese-cloth 

 or silk tapering bag, as used by the " Challenger " and many 

 other expeditions, to the more compHcated " closing " nets 

 of Agassiz, Nansen and other Scandinavian investigators, 

 which were designed to sample special zones of water below 

 the surface (Fig. 16). But the Kiel school consisting of Hensen, 

 Brandt, Apstein, Lohmann, and their disciples, introduced 

 more precise methods, and designed nets of definite shape 

 and dimensions which were calculated to strain a known 



