Algae. 607 



by the rivers, viz: Botryococcus Braunii, Oocystis Naegelii, Gompho- 

 sphaeria aponina, Microcystis aeruginosa, hottom.- DüitomSj but not 

 Coitj'tigatae. 



5. The phytoplankton of the Aral Sea may be divided in 4 

 parts, that of the North Bay, that of the surroundings of the Island 

 of Nicolaus, that of the South-Coast and that of the open Sea. 



6. The phytoplankton of the North Bay is in the springtime 

 characterised bj'' the abundance of Chaetoceras PF/^/irt;;z/accompanied 

 by Chrysomonadineae-s^oreSy Cyclotella caspia, Nitsschiella teniäros- 

 tris, Thalassiosira decipiens, Ebria tvipartita and Thitinnopsis cylin- 

 drica; in summer prevail Coscinodiscus oralensis, Cainpylodisctcs dae- 

 meliarms, C. echeneis, Melosira Borreri, Chaetoceras subtile and Di- 

 plopsalis caspica. From both spring and summer samples are to be 

 mentioned: Oocystis socialis, Diplopsalis pilhda, Gleuodiiiiimi trochoi- 

 deiini, Gonyaiüax Levanderi, Peridinium achrornaticuni, Actiiiocyclus 

 Ehrenbergii and other diatoms. 



7. The phytoplankton of the lagoons and bays of the Island of 

 Nicolaus is only known in high-summer. The characterislic species 

 are Peridinium subsalsum, Prorocentruni obtusuni, Coscinodiscus 

 aralensis, Actinocyclus Elirenbergii, Chaetoceras subtile, Diplopsalis 

 caspica, Gonyaulax Levanderi and Codonella relicta. 



8. Also the phytoplankton of the South Coast is onh' known 

 in high-summer; it is rather different at different places, but in 

 composition it comes nearest to that of Nicolaus-Island. with 

 some special forms in Utsch-utkul Bay, viz. Gonyaidax apicidata 

 var. Cleveij Oocystis Naegelii, Geminella niterrupta. 



9. The phytoplankton of the open Aral Sea in high-summer is 

 very poor; no species is distinctive for this area, the few forms found 

 are all at home in the coastal areas and occur in the open Sea in 

 scanty quantities, the plankton nearly consisting of Zooplankton alone. 



10. The phytoplankton of the whole brackwater area is büild 

 up from three catagories: a. freshwater organisms carried out in the 

 sea — all species of wide distribution; b. organisms of the brack- 

 water lagoons — some species of wide distribution, others endemic; 

 c. organisms of brackish sea-water, brackwater phytoplankton in 

 proper sense. 



11. When studying the distribution of the true brackwater forms 

 (23 species) outside the Aral Sea area, we find 12 species (53 per 

 Cent) ubiquious forms. Next come 6 (25 per cent) with rather wide 

 distribution in brackwater areas with relatively low salinity (Azov 

 Sea, innermost part of Baltic Sea, Zuider Sea). One species, 

 Campylodiscus daemelianus, occurs^ in the Ponto-Aralo-Caspian 

 area and besides in the coastal fegions of warmer seas. Lasth^ 4 

 species — Oocystis socialis, Coscinodiscus aralensis, Cyclotella caspia 

 and Diplopsalis caspica — are restricted to the Aralo-Caspian 

 area, but are each related to forms of much wider distribution. 



None of the forms characterising the phytoplankton of the 

 Aral Sea proper is endemic (but this is the case, with some of the 

 lagoon-forms, viz. Peridinium subsalsum, Prorocentrum obtusum and 

 Anabaena Bergii). 



12. The phj^'toplankton of the Aral Sea is probably of very 

 young origin, not surviving from the postpliocen time, and the 

 Immigration must have taken place over land. Living under such 

 special conditions as ruling here in the Aralo-Caspian area, 

 several forms have been differentiated and modified, but time has 

 not been long enough to produce much diverging characters. 



