ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 741 



dissolved salts is a function of very negligible importance, since the 

 author has convinced himself by numerous experiments that the presence 

 of a more or less thick stratum of mucilage does not at all, or at any 

 rate very little, delay osmotic movements across the membranes of 

 algas. 



Vegetation of the Upper Rhine.* — R. Lauterborn writes an in- 

 teresting account of the vegetation of the Upper Rhine. On account of 

 the swiftness of the current the algae can only live in the back waters, 

 where a rich micro-flora is developed. The Lake of Zurich is a very 

 important plankton-reservoir for the Rhine, and the Lake of Constance 

 is not to be undervalued. The traces of this latter lake are seen in the 

 Cyclotellre, which are the most richly developed of all pelagic organisms 

 in this lake. From these two basins of the Sub-Alps is poured a con- 

 tinuous stream of plankton into the Rhine of such species as can withstand 

 the destructive influences around, such as Diatoms and Geratium. Between 

 Basel and Mainz the flora is greatly enriched by species which are not 

 present in the lakes, and are supplied by the numerous old river beds, 

 inlets and harbours of the Rhine. The author gives a description of the 

 entire vegetation of the old river beds. He then treats of the biological 

 character of the river, which is not in the least that of a valley, but far 

 more that of a mountain water. He gives the names of the species 

 which bear out this statement. In the final chapter the author deals 

 with a good many individual species from the Lake of Constance and 

 from the upper waters of the river itself. 



Fresh-water Algae of Dutch New Guinea.f — C. Bernard gives an 

 account of the fresh-water algae collected jby Versteeg in New Guinea 

 during the first Dutch expedition under H. A. Lorentz. The material 

 was gathered at three stations, but is very limited in amount. The 

 Desmidiea? are few, and Protococcaceaa are absent. He discusses the 

 reasons for this. He enumerates twenty-three species and varieties, two 

 of each being new. A bibliography is included. 



Formation of Colonies in Flagellatse.f— A. Pascher describes certain 

 cases of ephemeral colony-formation in Flagellate. Of the phylogenetic 

 development of the colonies but little is still known, and the stages of 

 association described by the author may be regarded as the precursors 

 of the true colonies. The first observations of primitive colonies were 

 made on species of Chrysonionadese. One species of Chlamydomonas 

 was found in a palmelloid condition. The various stages of development 

 in the different species are described in detail. At first the cells resulting 

 from the first division remain loosely together, dividing later. Then 

 follows the second division, making a colony of four individuals. Since 

 the movement of the cilia remained unanimous, so long as the indi- 

 viduals were enclosed in a common sheath, locomotion formed no hind- 

 rance to the duration of such colonies. After the second division the 

 cells may either separate as in Ochromonas sociata, or they may divide 



* Ver. Natur. Medizin. Vereins Heidelberg, n.f. x. (1910) pp. 450-502 (2 figs.) 

 See also Hedwigia, 1. (1910) Beibl., pp. (53) (54). 



t Lorentz, Nova Guinea. Result. Exped. Sci. Neerlandaise. Leide : Brill (1910) 

 viii. 2, pp. 253-70 (2 pis.). 



X Ber. Deutsch. Bot. Gesell., xxviii. (1910) pp. 339-50 (1 pi.). 



