4 THE PLAl^KTOIf-PHASE AXD PLANKTON-BATE 



of what the sea has done for living organism, or what the latter realh'' 

 is in terms of sea- water ; while higher organisms may continually 

 revert to similar conditions of life, or pass through such recapitulatory 

 stages in their Life-History. In other words they may retain a 

 Plankton-Phase in the Life-Cycle. The ova and spermatozoa of higher 

 Metazoa thus represent a return to the ancestral condition of a pre- 

 ceding suspended Plankton-organization ; as do also the zoids both 

 asexual and gamete, mobile and immobile, of marine algae. Even 

 the highest animals retain in their spermatozoa the evidence of their 

 plankton-origin as marine flagellates, and acquire in this phase a 

 " plankton-value" (Prenant) ; only in most specialized types of land- 

 vegetation (Siphonogamic Phanerogams and a few Fungi) does the 

 sexual process, itself a plankton-mechanism, eliminate all direct 

 evidence of its marine origin. 



A purely empirical estimate of the autotrophic plankton of the 

 sea, based on the oljservations of Lohmann (Kiel, 1908), suggests the 

 possibility of visualizing a fair average plankton-rate as expressed by 

 the amount of cytoplasm in one million zoids per litre ; taking a zoid 

 of 5 /x diam. ("rounded off "), Avith apj^roximate volume of 100 c. /.i 

 as a standard. Such a value would be probably regarded as liberal 

 for the English Channel, as bearing reference to the prunar}'- auto- 

 trophic organism, more particularlv Diatoms and zoospores on which 

 more holozoic organisms depend ; though little is yet known of the 

 zoid life of the sea, or of anything conceivably still smaller ; since 

 there is so far no known method of collecting living organism of 

 fluid plasma, no denser than milk, and held more or less in spherical 

 form merely by the operation of surface-tension ; the same applies to 

 all algal reproductive cells, from the great oospheres of Ilimantlicdia, 

 300 jx diam., and visible to the naked eye, to the smaller zoids of 5 fx, 

 or so, continually emitted by the Green and Browni Algse. With such 

 a convenient unit, for example, it may be possible to express a 

 Laminarian producing 300,000 million zoids (Sacco7']iiza) as approxi- 

 matel}^ equivalent to the plankton of 300 cubic metres of sea- water ; 

 or to give a corresponding plankton-value to a tish, based on the 

 number and volume of its ova or spermatozoa. In this w^ay benthic 

 organisms may be compared with plankton-phases, and with each 

 other. Thus taking an estimate of 7 million ova at 1-39 mm. diam. 

 (Masterman, p. 23(3), a spawning cod of the same weight as the sea- 

 weed may be possibly regarded as returning plankton to 100,000 cubic 

 metres, or 100 million liti-es of sea-water ; though data from the 

 spermatozoa would be probabl}'' more reliable, as representing cyto- 

 plasm rather than food-material and oil, the idea is sufficient for 

 present purposes, and may be compared with an estimate for such a 

 fish in terms of 1 2,500 sq. metres of surface-area for the North Sea 

 (Johnstone, p. 171). Such a method of visualizing the reproductive 

 output of an organism is again of interest as enabling some sort of 

 rough comjjarlson to be established in the case of the later developments 

 of Land-Flora. The return of benthic organism to the flagellated 

 plankton-phase clearly expresses the wastage of the reproductive 

 processes, as included under " fertilization " and " dispersal " ; while 

 the further control and economv of such wasta":e becomes at once the 



