228 Marine A^icrobiology 



cellular organisms are often observed between 200 and 2,000 

 m. But another problem, as yet scarcely resolved, is to explain 

 those local fertilities. The only sure fact is that deep cells of 

 Cyclococcolithus have exactly the same skeletons as surface speci- 

 mens; i.e., rather heavy^ (probable densit}^: 1.23), such palmelloid 

 flagellates can dive, but adopt an heterotrophic physiology when 

 light is failing. 



REFERENCES 



Only four authors have pubhshed on the deep unicellular fertility. 

 We have chosen a small number of references, where other works are 

 quoted : 



1. Bernard, F.: Essai sur les facteurs de repartition des Flagelles cal- 



caires. Ann. Inst. Ocean., 21:29-112, 1942. 



2. Bernard, F.: Recherches sur le cycle du Coccolithus fragilis Lohm. /. 



du Conseil, 15:177-188, 1947. 



3. Bernard, F.: Eaux atlantiques et mediterraneennes au large de I'Al- 



gerie. II. Courants et nannoplancton de 1951 k 1953. Ann. Inst. 

 Ocean., 2i:231-324, 1956. 



4. Bernard, F.: Distribution verticale des sels nutritifs et du phytoplanc- 



ton en Mediterranee: essai sur I'epaisseur de la couche a photosyn- 

 these. R. & P. V. Comm. Int. p. I'expl. Medit., reunion pleniere de 

 Monaco, 1958. 



5. Bernard, F.: Plancton et benthos observes durant trois plongees en 



bathyscaphe au large de Toulon. Ann. Inst. Ocean., 35: fasc. 4, 1958. 



6. Bernard, F. and Legal, J.: Plancton unicellulaire recolte dans I'Ocean 



Indien par le "Charcot" (1950) et le "Norsel" (1955-56). Bull. Inst. 

 Ocean., 1:166, 1959. 



7. Hentschel, E.; Allgemeine Biologic des Siid-Atlantischen Ozeans. II. 



Das Pelagial der Unteren Wasserschichten. Berlin, Walter de Gruy- 

 ter, pp. 1-344, 1936. 



8. HuLBURT, E. M., Ryther, J. H., and Guillard, R. L.: The phyto- 



plankton of the Sargasso Sea oflF Bermuda. /. du Conseil, 25:115-128. 



9. Lacombe, H. and Tchernia, P.: Stations hydrologiques efiFectuees a 



bord de la "Calypso" en 1955 et 1956. Cahiers Ocean, du C.O.E.C, 

 li: (5-6), 1959. 

 10. Lohmann, H.: Die Bevolkerung des Ozeans mit Plankton wahrend des 

 Ausreise des Deutschland 1911, Arch- f. Biontologie, 4:1-600, 1920. 



