ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 453 



masses to the bottom of the sea. The author enumerates and describes 

 forty-six species of micro-organisms found by him in material collected 

 in the Adriatic in 1891 and 1905, during the phenomenon of the " Mare 

 Sporco." 



Fresh-water Algae among Marine Plankton.* — E. Lemmermann 

 discusses the behaviour of certain classes of algse on being removed from 

 fresh to salt water. He finds that most fresh-water plankton forms 

 disappear as soon as the salinity of the water is raised. In those fresh- 

 water plankton forms which do exist in salt-water it is worthy of note 

 that no remarkable change takes place in their floating apparatus ; and 

 this is borne out by the plankton of the less saline Baltic sea, which is- 

 not very dissimilar to that of the Xorth Sea. From these observations 

 the author concludes that the formation of longer or sliorter processes 

 does not depend exclusively on the greater or less specific weight. The 

 number of fresh-water forms observed hitherto in marine plankton is. 

 eighty-six. 



Algological Observations. t — X. "Wille publishes a series of notes on 

 some investigations made by him at Drontheim. The first is on the 

 development of Prasiola furfuracea, in which the author describes and 

 figures various stages in the life-history of an extreme form of that 

 species, which was shown to be identical with P. leprosa Kiitz. A 

 summer form of Ulothrix consociata Wille is next described, in which the 

 cell-walls are much thicker, more gelatinous, more retentive of water, 

 and show a more distinct stratification than in the spring form. The dis- 

 tinguishing points are described in detail. The third note is on a new 

 marine Tetrasporacea, which forms the type of a new genus Pseudotetra- 

 spora, under the name of P. marina. A new method of multiplication 

 in Gl(Bocapsa crepidinum Thur. is described, in which some of the cells 

 of the colonies divide up into cocci, which separate from each other Und 

 develop a mucilaginous cell-wall. The single cells are spherical with a 

 diameter of 2 • 5-3 /a. Each cell is surrounded by a transparent wall or 

 covering, which is rarely visible except when two of the free-swimming 

 coccus-cells collide. For reasons given in full the author considers that 

 Aphanocapsa marina Hansg. is only a developmental stage of GJceocapsa 

 crepidinum Thur. The remaining notes are entitled : On Dactylococcus (?) 

 litoralis Hansg. ; on the zoospores of Oomoiitia ])olyrhiza Born, et Flah. ; 

 and Littoral Myxophycege and Chlorophyceai from the surroundings of 

 Drontheim. 



Cytological Studies in Cyanophyceae.^ — N. L. Gardner publishes 

 the results of his researches on the cytology of the Cyanophyces, of 

 which he has collected and investigated more than 100 species. His 

 object was to settle certain points about which there has been much 

 controversy, viz. the presence or absence of a nucleus, its structure or 

 functions, the structure of the cytoplasm, the presence of chromato- 

 phores, and the nature of the granules. One of the chief difiiculties 

 which he had to overcome was the elimination of the sand that adheres. 



* Arch. Hydrobiol. u. Planktonk., i. (1906) pp. 409-27. 



t Kgl. Norsk. Vidensk. Selsk. Skrift. 1906, No. 3, 38 pp., 1 pi. 



X Univ. of California Publications (Botany) ii. (1906) pp. 237-96 (6 plates). 



