ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 499 



they rest on exact data. Only cultures arc described which deal with 

 pure material and are free of bacteria. Thus the results are biologically 

 exact. Chemical exactness was also obtained. It is seen that of 

 mineral constituents, K, Mg, 8, P, and perhaps Fe, are necessary. Occa- 

 sionally, as in higher plants, Ca is needed. Diatoms alone need Si and 

 Na. None of these elements can be entirely replaced by any other 

 similar one, though the quantities may be partially made up by the 

 addition of a nearly allied element. The meaning, of the excretion of 

 CaC0 3 by certain species is discussed. 



Coccolithophoridas from the Adriatic.*— J. Brunnthaler has col- 

 lected and studied these organisms at Rovigno, and records seven species 

 new to the district, one of them being also new to science, Syracosphaera 

 Lohmanni. In August and September the commonest forms at Rovigno 

 were Rhabdospheera stylifer, Syracosphsera pulchra, S. robusta, S. medi- 

 terranea, S. spinosa, and Pontosphsera inermis. Noteworthy is the absence 

 of the genera Scyphosphsera and Goccolithophora. The shortness of the 

 time at the author's disposal for collecting mav, however, be the cause of 

 this. 



Two Russian Chrysomonads.f — S. M. Wislouch records two species 

 of Chrysomonadeae new to Russia, Synwra reticulata Lemm. and Pala- 

 tinella cyrtophora Lauterb. He gives the dimensions of the latter 

 species. On account of the smaller size of the cells, the author designates 

 his find as a new form, P. cyrtophora f . minor. He gives a figure of it. 



Euglena viridis.J — H. Wager has made some experiments on the 

 effect of gravity upon the movements and aggregation of Euglena 

 viridis and other micro-organisms. He finds that, when placed in the 

 dark in shallow vessels or narrow tubes, a peculiar aggregation of these 

 organisms takes place into net-like patterns or more or less well-defined 

 circular groups. The aggregation is only visible when the Euglena? 

 are abundant, and is more regular and pronounced in a shallow vessel 

 than in a deep one. Each group shows clearly two distinct regions, a 

 centra] denser one, consisting of cells moving downwards, and a lighter 

 peripheral area, consisting of cells moving more or less regularly up- 

 wards. This constant cyclic movement is kept up so long as the aggre- 

 gation persists, and this may be for several days. In a good light the 

 aggregation soon disappears, 1 tut reappears again in a few seconds when 

 placed in the dark. If it be disturbed by the shaking of the vessel, it is 

 re-formed immediately the disturbance has ceased. The aggregation does 

 not appear to be due to currents set up in the liqnid either by heat or 

 evaporation; nor upon the presence or absence of oxygen or carbon 

 dioxide, except in so far as these may be necessary to maintain the 

 motility of the organism. The downward movement appears to be a 

 purely mechauical one. Experiments were also made with Euglena deses, 

 Ghlamydomonas, Volvox, Spirillum, and one of the fresh-water Peridinieaa, 

 in all of which the phenomena were visible, but with considerable varia- 

 tion in the extent to which it was produced. The author finally points 



* Internat. Rev. gesamt. Hvdrobiol. u. Hvdrogr., iii. (1910-11) pp. 545-7. 

 t Bull. Jarcl. Imp. Bot. St. Petersbourg, x. (1910) pp. 1S1-5. 

 X Proc. Roy. Soc, ser. B., lxxxiii. (1910) pp. 94-6. 



