Z THE PLANKTON-PHASE AND PLANKTON-BATE 



its original sense involved a physiological rather than a morphological 

 conception, and relates to the problem of the food-supply of the sea ; 

 and it is in this sense of " primary food-supplj^," the base of the 

 ** marine pyramid of life in the sea," that the Avord should be always 

 considered, and its meaning further limited as required ; the spirit of 

 the expression being more significant than the letter. Thus, omitting 

 smaller fishes, Salpie, Medusae, Fish-ova, Copepods, Nauplii, and other 

 larval forms, and everything holozoic that lives by eating somebody 

 or something else, the expression really reduces to the suspended 

 aidotro'pliic vegetation of the sea, on which ultimately the great mass 

 of heterotrophic life depends ; and whatever connotation be given the 

 term in zoological Avork, the botanical sense is perfectly clear and 

 defined, as the subject is essentially a botanical one. The word 

 reduces, according to Hensen's original conception, to the free uni- 

 cellular forms of plant-life, maintained in suspension in pelagic 

 water ; anj^ extension to such forms living anywhere else is purely 

 metajDhorical and secondary ; while its application to animal forms, 

 eating the plants and each other, represents an equally secondary and 

 crude application in another direction ; a convenient convention so 

 long as all the forms are captured together, and by the same methods. 

 The difficulty is increased by the fact that in many cases it is still 

 vague to -what extent nutrition may be dominantly holophj^tic or 

 holozoic : thus, the vast bulk of pelagic ph^^toplankton consists of 

 Diatoms ; to a lesser extent, under conditions usually of diluted sea- 

 water, of C^^anophyceae, and to a considerable extent of Peridiniaceaj 

 aud G-3'mnodiniacese, all more or less holozoic ; as also of Flagellate 

 races as Brown Chrj'somonads, Coccolithophoridse, Cryptomonads, and 

 green Chloromonads, the majority of which are probably at least as 

 much holozoic as holoj^hytic. 



The amount of plankton -life possible in sea-water is almost in- 

 credible, since it is invisible to the exQ except in special cases, as when 

 the colour of the water is affected. Thus Gran records the water of 

 Christiania Fjord (1911) as showing a milky tint with Fontosp}i(sra 

 Huxleyi (a Coccosphere), at the rate of 5-6 millions per litre. 

 Moseley (1879, p. 5Q^) on the 'Challenger' describes the water of 

 Arafura Sea, supplied hj the large rivers of New Guinea, as brown 

 and smelling like a stagnant pond with Tricliodesmium (Cj'anophj'-ceaj); 

 the " black-water " of the Arctic Seas, the haunt of the Eight Whale, 

 for stretches of 50-100 miles, may be deep black and opaque, or again 

 grass-green, apparently mainly due to Diatoms (Robert Brown) ; 

 Peridiniacese, as GonyaulaXy may turn the sea to blood (Bombay, 

 California, Australia), killing the- fish by removal of free oxygen 

 (Carter, McClendon). As a rule, maximum plankton-content occurs 

 where coastal waters bringing salts and land-debris meet thoroughly 

 aerated and relatively bacteria-free oceanic water, and the deep blue of 

 the ocean is characterized by a poor flora and fauna. Thus the green 

 w^ater of the North Sea is richer than the Atlantic, and the summer- 

 heated, shallow and silty Baltic, more than half-fresh, supplies the 

 richest plankton known. The detailed observations of Lohmann 

 (1908) for the highly nutritive water of Kiel Bay afford the standard 

 for further investigation, and are sufficiently thorough to give a very 



