THE PLANKTON-PHASE AND PLANKTON-RATE. 

 By a. H. Chuech. 



The term Plankton, proi30sed by Victor Hensen of Kiel (1887), 

 for the floating population of the sea (7rAayK7-os=roaming ; i. e., in a 

 moving medium, not merely passively suspended) was established by 

 the classical researches of the Plankton-Expedition of the Steamship 

 'National' (1889), published in many volumes from 1892 on, as 

 representing a fundamental conception of the greatest biological 

 significance, though still very inadequately recognized by botanists in 

 this country. Like other satisfactory and picturesque terms the word 

 has been much abused b}^ lesser lights, and diverted from its original 

 intention in marine biology, more particularly by land-botanists. A 

 subject of primarily pelagic interest has been degraded to the paltry 

 notion of the " Limnoplankton " of a pond, the " SajH-oplankton " of 

 dirty water, and to such curious expressions as the " Cryoplankton " of 

 algae found on snow (Warming) ; while a similar analogy might 

 suggest " Dendroplankton " for Pleurococcits living on the bark of a 

 tree, or for Diatoms on the leaves of a tropical rain-forest. Though 

 such usage may be justified in a minor degree when the true signi- 

 ficance of the word is fully understood, such subsidiary variants must 

 not be allowed to obscure the original meaning of the term, and the 

 almost infinite magnitude of the problems it ' covers. A certain 

 amount of perspective may be demanded ; otherwise, as Bunthorne 

 would say, Ave look for oceans and find puddles. 



A preliminary idea of the subject may be gained by the considera- 

 tion of the sea as seen in summer from any headland on the British 

 coast, or by watching the breakers rolling in as apparently mere blocks 

 of water, and remembering that every drop of these seas contains at 

 least one living organism, and that the amount of water in sight, 

 within the range of only a few miles, is but an insignificant fraction 

 of the Narrow Seas for which the same generalization would hold. 

 The organisms being fewer in bottom water, beyond 10 fathoms, but 

 many more at the surface ; a *' drop " of water being taken as -^j^ c.c, 

 and containing 50 c.mm. 



The term Plankton, again, originally understood as including 

 anything taken by Hensen's vertically hauled hoop-net, with aperture 

 of one square metre, and constructed of fine bolting-silk, the open 

 meshes of w^hich are 40-50 yw. diam., is again somewhat vague, since 

 larger organisms may evade the net, and the smallest, often in the 

 majority, may slip through; hence net-observations afford only a 

 rough idea, and the centrifuge (Gran), and filters (Lohmann), or 

 actual cultures (Allen) have been employed for finer work. But the 

 extension of the term to '* Macrophytoplankton " for floating Angio- 

 sperms, or to material which might in the limit include a dead whale 

 or the Sargasso-weed, is clearly beyond the original intention of the 

 term; and such innovations as '* Seston " (Kolkwitz) to include in- 

 Organic detritus, only tend to obscure the main issue. The word in 

 Journal of Botany, June, 1919. [Supplement III.] 



