534 



NATURE 



[October 13, 1923 



made to increase our knowledge of the siil'i<. t As 

 the middle part of the southern basin will not be 

 drained, but remain open water, named Lake Flevo, 

 we shall have a splendid opportunity of studying the 

 changing of the brackish-water fauna into a fresh- 

 water community. We do not know how long this 

 will take, but, seeing the amount of water that is 

 brought to the Zuiderzee by the river Yssel, it is 

 almost certain that the days of the brackish Zuiderzee 

 will be counted as soon as the dike between the pro- 

 vinces of Holland and Friesland from Wieringen to 

 Piaam is ready, which will take another ten years. 

 Nevertheless, we must be very glad that the research 

 work has begun in such splendid style. 



In the first chapter, the geology and hydrography 

 are treated by Steenhuis and Redeke respectively. 

 The geology is, of course, for the most part based on 

 historical facts, as we know that two thousand years 

 ago there was no Zuiderzee, but a Lake Flevo, as there 

 will be again at the end of this century. The reason 

 for this victory of the sea over the land must lie in 

 the change in relative height of land and sea-level. 

 The author does not give his opinion, however, about 

 the cause of these changes. The hydrography, treated 

 by Redeke, is of extreme importance, as we find here 

 tables of temperature and salinity of the water in 

 different parts of the basin during all seasons of the 

 year. The lowest salinity (4 to 8 -per mille) is found 

 along the east coast, where the Yssel water flows, and 

 causes a constant stream in a northerly direction. 



The flora of the Zuiderzee is treated by Dr. van 

 Goor, and the halophytes and submerged Phanerogams, 

 the Algse, and the phytoplankton are dealt with suc- 

 cessively. Some fifty species of Algse were collected, 

 among them some that were previously unknown in 

 the Dutch flora. The most important, however, is 

 a new form of Fucus, baptised F. intermedius, nov. 

 spec, which is intermediate between F. vesiculosus 

 and F. platycarpus , and still not to be identified with 

 the Fucus ceranoides, the brackish-water form of the 

 French coast, which occurs also in the Schelde River. 

 It should be of great interest to study the Fucus 

 growth in Breydon Water, Hudson Bay, etc., to com- 

 pare and try to find out more particulars of the dis- 

 tribution and life-history of this interesting group. 



A comparison between the flora of the Baltic and 

 Zuiderzee gives the interesting result that, while in 

 the Baltic Cyanophyceae and Peridiniales form by far 

 the greatest part of the planktonic organisms, in the 

 Zuiderzee the Diatoms play the most important role. 

 The Copepod fauna of the Baltic and the Zuiderzee 

 is much the same, but in the phytoplankton there is a 

 difference even in the genera of the most important 

 species. 



NO. 2815, VOL. I 12] 



The Protozoa arc treated by Hofker, who gi\.v 

 a well-illustrated review of the specimens collects 

 which is of great value, as hitherto ver>' little wi.;; 

 has been done in Holland on these groups. Especiali . 

 his account of the Foraminifera will prove a great -.'■ i 

 for further investigation. It is highly prol)ablc tl.a 

 this shell-bearing group will furnish in later years ju t 

 as good methods for analysing alluvial and dilu\ I 

 deposits as diatoms already give. It is a great pt 

 that the publication is merely systematic and moqjh. 

 logical, for comparison with other faunas -ind 

 partition in salinity groups woulfi have been 

 greatest importance. We hope that this part oi tijc 

 work will follow, and point out that van Goor did it 

 for the flora, Funke for the hydroids (twelve specie > . . 

 Geertje de Lint for Cladocera and copepods, etc. 



Dr. de Man treats the free-living nematods, and 

 describes among his forty-nine species no less than 

 twelve that are new for science. For particulars I 

 must refer to the publication itself. Twenty spec ii^ 

 of polychaet annelids were collected, and are treated 

 by Dr. Horst ; five species of Oligochaetae, described 

 by Nel de Vos, while Dr. Wibaut-Isebree Moens shows 

 that several Rotifera occur in fresh as well as in 

 brackish water. Then we come to that important 

 group, the Crustacea, important from the fisherman's, 

 and therefore from the scientific point of view, as thcv 

 have been very thoroughly studied recently. I ha\c 

 already mentioned the Cladocera and Copepoda, 

 studied by Geertje de Lint. A new species of Schiz- 

 opera is described. 



Spongise, Cirripeda, Isopoda, Amphipoda, and 

 Schizopoda are all treated, but show no special char- 

 acters. Among the Decapoda, analysed by Dr. J. J. 

 Tesch, Leander longirostris, called the Rhineprawn 

 by British carcinologists, was found only once in the 

 Zuiderzee. The life - histor}' of the specific little 

 Zuiderzee crab, Meter opanope tridentata, is very in- 

 teresting ; its only allies live in the tropical Pacific, 

 and it has not been studied before. Illustrations of 

 the larval states will prove ver}' useful in recognisim: 

 this interesting little creature. 



A new Acaris is described by Oudemans ; Having;.! 

 treats the marine MoUusca, of which several are >>! 

 importance, as food for fishes and men. Cardium 

 edule and Mya arenaria have tj-pical brackish-water 

 forms and measures. Among the fresh- and brackish- 

 water MoUusca treated by Tera van Benthem Jutting 

 is the famous Corambe batava, Kerbert, found for the 

 first time in 1881 ; it appears to be not at all rare on 

 the Zostera meadows of the Zuiderzee. Eggs and 

 radula are described and represented. Assemania 

 grayana appeared to be a sexual dimorph, the male 

 being much smaller than the female, and being usually 



