22 Algae. 



c'est le nombre considerable des formes septentrionales qu'elle 

 contient (40 environ), communes ä la Mer du Nord, ä l'Ocean 

 Atiantique ou Arctique, mais inconnues dans la mediterranee. 

 Mr. Mereschkowsky, voit dans ce fait une preuve tres 

 serieuse ä l'appui de la theorie, un peu abondonnee actuellement, 

 qui admettait que la plus grande partie de laRussie centrale 

 etait occupee, ä l'epoque glaciaire, par une vaste mer qui 

 s'etendait jusqu'ä la Mer noire, la Mer Caspienne et la Mer 

 d'Aral, reunissant ces trois bassins, aujourd'hui isoles ou presque 

 isoles, avec la Mer du Nord et l'ocean glacial. 



Une planche separee et deux figures dans le texte sont jointes 

 a ce travail. P. Hariot. 



Petersen, C. G. Joh., DeDanske Farvandes Plankton: 

 Aarene 1898 — 1901, I. (The Plankton of the 

 DanishSeas during the vears ofl 898—1 901.) (Kgl. 

 Danske Vidensk. Selsk. Skrilter. Ser. 6. Voi. XII. 1903. 

 p. 223—262.) 



The director of the Danish biological Station, Dr. C. J oh. P e t e r s en, 

 has arranged a thorough investigation of the plankton in the sea around 

 D e n m a r k during the years of 1888 — 1901. Plankton-samples were collected 

 every fortnight during these three years and from 10 places (for the most 

 part from light-ships), situated in the North Sea, the Skager Rack, the 

 Kattegat, the Belt Sea and the Baltic Sea. 



The plankton-net used were 1. afunnel-shaped tovv-net of 

 30 ctm. diameter and Millergauze No. 19, 2. a closing-net, invented 

 by Dr. Petersen, with Millergauze No. 19, 3. an egg-net, Millergauze 

 No. 0; all the hauls were vertical. 



The main results are the following: 



1. The greatest density of the plankton has been found in the baltic 

 water in the Kattegat and the Belt Sea. 



2. The greatest density is allways due to a great quantity of dia- 

 toms, and this quantity mostly occurs in shallow water and near to the 

 coasts 



3. The water of 34 — 35''/o salinity which fills up the Skager Rack and 

 the deeper parts of the Eastern Kattegat has always a very low density 

 of plankton. 



4. The plankton in the Baltic Sea east of Gjedser-Dasserort is 

 allways very poor, while the western Baltic Sea is more allied to the Belt 

 Sea and the Kattegat. 



5. From December to February the density of the plankton in Katte- 

 gat is very low, and this is the darkest and partly the coldest season. 



6. The density in Kattegat has a spring-maximum and an autumn- 

 maximum, caused by the enormous multiplication up of the diatoms ; in 

 the Summer the Peridiinaceae predominate in the open Kattegat, but 

 along the coasts the diatoms prevail throughout the year. 



The remaining part of the paper deals with the Zooplankton (fish- 

 eggs, fish-larva etc.). C. H. Ostenteid. 



ROWLEV, F. R., Some points in the Structure and Life- 

 History of Diatoms. (Journal of the Quekett Micro- 

 scopical Club. Ser. II. Vol. VIII. April 1903. No. 52. 

 p. 417—430. pl. 23. 5 figs. in text.) 



The author here gives a füll abstract of that part of Lauterborn's 

 „Untersuchungen über Bau, Kerntheilung und Bewegung der Diatomeen", 

 (Engelmann, Leipzig, 1896), which relates to the protoplasm and its 



