20 Algae. 



Cleve, P. T., Plankton Researches in 1901 and 190 2. 

 (K. Svenska Vet. Akad. Handl. Bd. XXXVI. No. 8. 1903. 

 March 12. p. 53.) 



During the years of 1901 and 1902 Professor Cleve has continued 

 his examination of plankton-samples, collected at the West-Coast of 

 Sweden, in the Skagerak and in the North-Sea ; he gives now a report 

 of the results concerning the whole year of 1901 and of 1902until August; 

 from that date the international Cooperation for the exploration of the 

 sea has commenced work, and the later researches are to be for- 

 warded to the Central Bureau of the Cooperation. 



The researches contain the usual crowd of facts with regard to the 

 distribution (geographical and seasonal) of the plankton-organisms, 

 for which 1 must refer to the lists in the treatise. It is of more general 

 interest to mention the author's reply to Dr. Gran's*) attack of his 

 theory „that the plankton organisms continually drift with 

 the currents to far distant regions"; against that theory Dr. G ra n 

 maintains: „that the plankton develops on the spotswhere 

 found by the sprouting of re s t in g -s p o r e s, eggs etc.". It is 

 to regret that Professor Cleve generalises Dr. Gran's views in such a 

 way; because it is only with regard to the neritic planktonforms, that 

 Dr. Gran has pointed out that they must develop principally on the spots; 

 for the oceanic forms he admits the drift with the currents, and he does 

 not deny that sometimes neritic forms also are driven with currents. 



The Chief difference is, that Professor Cleve believes that the res- 

 ting spores may drift as well as the vegetative stages, while Dr. Gran 

 means that they are sinking down to the bottom and rest there until the 

 circumstances for sprouting become favourable ; Cleve' s hypothesis is 

 based upon the smallness of the spore and upon the spines, bristles or 

 hairs on their surfaces. In his argumentation we meet with the following 

 interesting point viz. that the theory of relics in the Baltic Sea from 

 the glacial epoch is not applicable to the marine forms of the bottom- 

 fauna, because they could not have endured the fresh water of 

 the Ancylus-sea. He means that the arctic forms have been introduced 

 to the Belt Sea and the Baltic Sea in the present epoch by means of 

 arctic currents. 



Unfortunately Professor Cleve's many new and interesting views 

 are not explained at length and it is hoped that he may explain them 

 more thoroughly in future papers. C. H. Ostenfeld. 



Mereschkowsky, C, Les types des Auxospores chez les 

 Diatome'es et leur evolution. (Ann. Sc. natur. Botanique. 

 Serie VIII. XVII. 1903. p. 224—262. 20 fig. dans le texte.) 



Les Premiers travaux relatifs aux Auxospores des Diatome'es sont 

 dus ä Thwaites (1847) et ä Lüders (1862). Tout recemment 

 G. Karsten s'est occupe de cette question et les resultats auxquels 

 il est arrive marqueront une epoque dans l'histoire de nos connais- 

 sances sur la reproduction des Diatome'es. 



En etudiant les faits tels qu'ils sont presentes dans les ouvrages 

 de Karsten, Mereschkowsky est arrive ä les Interpreter diffe- 

 remment. Pour lui la Classification naturelle des auxospores, d'apres leur 

 mode ou formation, serait la suivante : 



1. Auxospores asexuelles, se formant sans copulation et d'un 

 seul individu : 



Type 1. Auxospores se formant d'une seule cellule mere avec 

 un sous-type derive du type sexuel (Anaraphide'es, Nitzschia paradoxa, 

 N. Palea). 



Type 2. Deux auxospores se formant d'une seule cellule mere 

 (Bacilloide'es). — Deux sous-types : nucleus se divisant temporairement 



") See the abstract in Bot. Centralbl. Vol. XC. 1902. p. 671. 



