-,f(' 







19 



. ,-^, ,. -^, iL'Iiiz'osolcnla sti/li- 



4- 'Styh-Plankton (symbol S). Typical forms ,. . 

 ■' ^ Ji. ^ fonms 



iCeratium tripos, 



0. Tripos-Plankton ~ Tp „ ., h^h'izosohnia (data f. 



\ gracillima 



Neritie Types 



1- Southern Neritie i 



^ I'lnkton (symbol Nm). Typical forms ( -^ 



(Skeletonema costa- 

 tum, Leptoqjlin- 



2 



^^orthern Neritie 







Plankton 



- Ns 



8. 



Arctic Neritie 







Plankton 



- Ng 



4. 



Coneinnns Plank- 







ton . . 



Ne 



5. 



Halosphffira 







Plankton 



- Nh 



H J5 



drus danicus 

 Chadoccros furcella- 



tuni. Fragilaria 



oceanica 

 {Coscinodisciis concin- 

 I nus 



H(dosphwra viridis 



^Ve will first refer to the Oceanic Types. 



As M'e have already stated, the {'onditions in the open sea are 

 Similai' thronghout great stretches of ocean, and it commonly hap- 

 pens that one species predominates to such an extent as to deter- 

 "iine tlie nature of the Plankton. Therefore such a classification 

 '^ that made out by Cleve is practical and appbcal)le in many 

 ^stances, even if one differs from him in the hypotheses attached 

 to it. 



-I'efore jn'oceedini^' further, we would remark that Cleve's type, 



'''a-Plankton, includes Oceanic (Coscinoddscus) and Neritie (Tha- 



(fssiosira) forms. For tlie oceanic, one ought therefore to establish 



new type, Disco-Plankton, and place Sir a-Pla n kton amongst 



tlie Neritie forms. 



With this change. Cleve's ,t tvpes naturally embrace the 5 

 ^gie iJiatoms which, also, from our observations, most generally^ 

 occur as prevalent species in the Plankton. 



We tl 



I. 



2. 

 3. 

 4. 

 5. 



ms get: 



Disco-Plankton 

 Tricho- Plankton 

 Chseto-Plankton 

 Styli-Plankton 

 Tripos-Plankton 



Co.^einodiscut; oculus iridin 

 Thalassiothrix longissima 

 Chwtoceros decipiens 

 Rhizoso leni a s tyliform is 

 lihizosolenia alata 



thesi 



A (kidding question as to the correctness of Ci^eve's hypo- 



s concerning the movements of the Plankton may be put, viz., 



ler a type of Plankton — or Plankton (;ommunity if we may 



■I term employed for the fi.ved plants — ea,nnot become spread 



bcr ways than by means of the ocean currents. If Cleve's 



•^"^.y were right, it surely ought to be proved that the Diatomic 



"unities cannot spring up to any great extent in parts remote 



otliei-, even if the natural conditions were similar. In such 



_ case one might, justifiably talk, tor instance, of Clncto-water and 



-\\ater, in which the organisms could be regarded in the 



'f?bt as leading fossils in geological strata. 



The Swedish scientists have not endeavoured to being forward 

 any proof, of this being so, and, in reality, such could not be done. 

 On the contrary, Cleve's own tables shew us the possibility of such 

 independent develojiment. 



If but quite small numbers, for instance of Chseto, Disco and 

 Tricho Plankton species could be found amongst an abundant Styli- 

 Plankton, the possibility is raised of the other species becoming 

 gradually developed at the expense of the Styli-Plankton when 

 the waters cool or possibly undergo other, but hitherto unknown 

 hydrographical changes. The opposite would occur by an increase 

 of warmth, and even in the Polar current itself a Styli-Plankton 

 might gradually become developed provided it contained some in- 

 dividuals ot RMzosolcnia di/liformis which had survived the cold, 

 or which might enter it from adjacent currents. 



If we regard Cleve's Table I [97] in which he has placed a 

 number of, in his opinion, typical samples of Styli-Plankton 

 from the most different portions of the Atlantic, we will perceive 

 tluit in the 1 2 samples the following were met with. 



Styli-Species 

 Chseto- — 



Tricho- — 

 Tripos 



Chffito-Speeies 

 Disco- — 



Tricho- — 



Styli- — 

 Tripos- — 



lihizosolenia styliform/is . was found in 10 samples 



[ Chcetoceros horeah „ „ - 4 — 



I — decipiens ...... „ - ti — 



( Thalassiothrix longisdma ,, „ - ,5 — 



I Rhizosolenia semispiiia . . ,, „ - .3 — 



Rhizosolenia gracillima . „ ,. - 4 — 



In Table II, 7 Types of Clia>to-Plankton 



Chcetoceros boreale was found in 7 samples 



decipiens 



Coscinodiscus oculus ii-idis 

 Th'ila^siothrix longissima. . 

 Rhiz jsolenia semispina . . . 



— styli form is . . 



— gracillima . . 



7 

 1 

 5 

 4 

 5 

 4 



Of Trieho-Plankton, p. 6, 10 Typical samples 



Ti'icho-Species 

 Disco- — 



Chseto- — 

 Stvli- — 



( Thulassiothrix longissima . 

 \ Rhizosolenia semispina . . . 



Coscinodiscus oculus iridis 



( Chwtoceros boreale 



\ — decipiens 



Rhizosolenia styli form/is . . 



was found in 6 samples 



.0 



2 

 ,3 

 2 

 3 



It will be seen that even in tliese samples which Cleve him- 

 self has chosen, there are sufficient of tlie other Plankton Com- 

 munities to allow of their becoming developed when a change in 

 the conditions of existence oceui'red. 



In nature, the communities are, in most instances, even still 

 more mixed, even when one predominates. If one refers to our 

 PI. 4, Fig. 1, it will be seen that at Station V, the Chajto-Plank- 

 ton predominates, with Tricho- and Disco-Plankton in a subordinate 

 degree. At Station VI, the same exists. At Station VII the three 

 Oceanic types are equally developed. At Station ^T^I, the Disco- 

 and Tricho-Plankton predominates, with Ch;eto- and Styli-Plankton 

 to a subordinate extent. 



