356 DEPTHS OF THE OCEAN 



multitude of species was surprising, though none of them was 

 very numerously represented. Every day one might sit and 

 examine some unique microscopical form, which might be lost 

 only too easily, and consequently had to be drawn there and 

 then. And whereas in the north there are large quantities of 

 every species, so that it is easy to investigate them in all their 

 stages of development and variation, this multiplicity of forms 

 in the tropics renders it incomparably harder to find out what 

 stages of development belong to the same species, or how the 

 boundaries between the different species are to be fixed. 



The various stations did not differ much from one another, 

 if we except Station 59, near Fayal in the Azores, where there 

 were numbers of neritic diatoms, and Station 66, close to the 

 Newfoundland Bank, where there was an addition of arctic 

 forms. On the whole, the multiplicity of species increased as 

 we went westwards. Possibly considerable differences may 

 be revealed when the material has been completely treated, but 

 all the species occur too sparsely in these samples to justify 

 one in drawing conclusions from negative results.^ 



The Tropical Atlantic flora much resembles the plankton 

 flora of the Indian Ocean observed by Karsten. In the Pacific 

 there would seem, according to Kofoid, to be an even greater 

 multiplicity of species, but I found several of the new species 

 obtained by him during the "Albatross" Expedition, and it is 

 probable that more and more of these rare Pacific species will 

 gradually be found within Atlantic waters also. 



In conclusion, it should be stated that, as far as quantity 

 is concerned, the smallest plankton organisms, Lohmann's 

 Nanno-plankton, play a far more important role than the whole 

 of the other species caught in our silk nets, which will be 

 subsequently discussed in their proper order. 



^ To show the character of the flora I append a list of species found at Station 64, lat. 34° 

 44' N. , long. 47° 52' W. , in a closing-net sample from a depth of 2CX) metres to the surface : — 



Diatoms : Coscinodiscus rex, C. Hneatus, Euodia cuneiformis, Planktoniella sol, Gosslenella 

 tropica, Thalassiosira stibtilis, Asterolatnpra tnarylandica, Rhizosoleniacastracanei, R. acuminata, 

 R. styliforinis, Bacteriastrum elongatuin, HemiaulKS sp., Chatoceras diclmta, C, tetrastichon, 

 C. peruviaman, C. coarctattiiii, C.furca. 



Peridinese : Ceratium pentagonum, C. teres, C. candelabrum, C. gravidum, C. fusus, 

 C. extensuin, C. pennattmi, C. gibberutn, C. buceros, C. platycorne, C. azoricum, C. ienue, 

 C. pavillardi, C. karsteni, C. declinatuin, C. gracile, C. arietinum, C. macroceros, C. massiliense, 

 C. arcuatum, C. ca}-riense, C. reticulatum, C. trichoceros, C. pahnatum, C. limidus, C. pulchellum, 

 species of Peridinium, Diplopsalis lentictda, Blepharocysta splendor maris, Ceratocorys horrida, 

 Goniodoma polyedricum, G. Jlvibriatum, Gonyatilax polygramma, G. joliffei, G. pcuifica, 

 G. fragilis, G. mitra, Protoceratium retictdatum, Podolampas elegans, P. palmipes, P. bipes, 

 Oxytoxum scolopax, 0. retictdatum, O. cristatum, O. milneri, O. tesselatum, Dinophysis 

 uracantha, D. schiittii, D. schrdderi, PJialacrotna argus, P. doryphorum, P. cuneus, P. rudgei, 

 Amphisolenia palmata, and another new species, Ornithocercus quadratus, O. magnificus, 

 O. steinii, O. splendidus, Pyrocystis lunula, P. noctiluca, Hexasterias problematica. 



CyanophyccEe : Trichodesmium thiebauUi. 



