Algae. 46 t 



auseinanderrücken, um die beiden Tochterkerne erzeugen zu 

 helfen. Eine Längsspaltung der Chromosomen konnte beim 

 Theilungsvorgange des Centralkörpers nicht beobachtet werden. 

 Mit der Centralkörpertheilung zugleich vollzog sich auch die 

 Zelltheilung, indem eine ringförmig angelegte Tochterscheide- 

 wand allmählich in's Zelllumen vordrang. Gleichzeitig schnürte 

 sich die Grundsubstanz des Centralkörpers in der Mitte unab- 

 hängig von der nach innen vordringenden Zelltheilungswand 

 ein,' wobei in dem isthmusartigen Verbindungsstück häufig feine 

 Spindelfasern sichtbar wurden. Der Centralkörper ist nach 

 allen diesen Beobachtungen als echter Zellkern aufzufassen, 

 dessen Theilung auf mitotischem Wege verläuft, zugleich aber 

 Anklänge an Amitose zeigt. M. Koernicke. 



LEMMERMANN, E., Das Plankton schwedischer Gewässer. 

 (Arkiv f. Botanik, utg. af K. Svenska Vet. Akad. Stockholm. 

 Bd. II. No. 2. 1904. p. 209. 2 pl.) 



The Svvedish botanists, Dr. 0. Borge and Prof. Dr. O. Nordstedt, 

 have collected numerous plankton-samples indifferent lakes in S w e d e n 

 (mostly in the southern part); all these samples have been examined by 

 the German planktologist E. Lemmermann, who publishes the result 

 of his examination in this paper. 



Of his more general conclusions we may mention: 



1. The Schizophyceae which produce aquatic flower, are fonnd in 

 many lakes. 



2. The most common Chlorophyceae are Boiryococcus Braunii, Eu- 

 dorina and Gloeococcus mucosus. 



3. The Desmids occur rather commonly, but not in large quantities. 



4. The Flagellates (especially Diplosigopsis and Dinobryon) are 

 often predominant. 



5. The Diatoms and Ceraüum hirundinella are often predominant. 

 A great part of the paper consists of tables and enumerations of the 



species found in each of the many samples, arranged after the localities. 

 The author gives a short characterization of 42 lakes after the predominant 

 plankton forms, dividing the limnoplankton in 4 types after the presence 

 or absence of Schizophyceae and Ceraüum hirundinella. 



There is a chapter concerning systematical remarks on 

 some species. The plankton-forms of the genera Oocystis and Te- 

 traedron are revised, a new genus Ecliinosphaeridiuin Lemm. is descri- 

 bed; also systematical remarks are added to some of the flagellates 

 (e. g. Mallomonas Hyalybryon, Dinobryon and Phacus), further a new 

 genus Peridiniopsis Lemm. Lastly the author attempts to arrange the 

 solitary species of the genus Chaetoceras, however without success. 



An enumeration of all the plankton-algae hitherto known from 

 Sweden and their localities finishes the paper. 



New names: Chroococcus limneticus, var. carneus (Chodat) Lemm. 

 var. fuscus nov. var.; Chr. minimus (Keissler) Lemm. and Chr. dispersus 

 (Keissler) Lemm. ; Oocystis gigas var. Borget nov. var.; Echinospheridium 

 Nordstedtii nov. gen. et spec. ; Diplosigopsis frequentissima (Zach.) 

 Lemm.; Mallomonas elegans nov. sp. ; Synura reticulata nov. sp.; Dino- 

 bryon utriculus var. Tabellariae nov. var.; D. Borget nov. sp. ; C. sueci- 

 cum nov. sp.; Hyalobryon Borgei nov. sp. ; Euglena acutissima nov. sp.; 

 Lepocinclis Steinii var. suecica var. nov.; Phacus Nordstedtii nov. sp. ; 

 Ph. moniliata var. suecica nov. var. ; Peridiniopsis Borgei nov. gen. et 

 spec. ; Chaetoceras distinguendum nom. nov. (= C. clavigerum Ostf.) ; 

 Ch. subsalsum nov. sp. ; Ch. Borgei nov. sp. 



The two plates illustrate most of the new forms as well as the 

 variations of Ceratium hirundinella. C. H. Ostenfeld. 



