474 Algae. 



rial, Means to prevent this drawback were found in the author's 

 proposal: to add 1:20 of F le m ming's strong Solution to the sea- 

 water samples. Such a preservation permits the examination of the 

 killed organisms of nearly all kinds, CoccolUhophoridae and several 

 naked infusorians and flagellates excepted. 



The examination of the numerous samples sent from the parti- 

 cipating countries, was made by the author, assisted by Miss Ca- 

 roline Leegaard and Miss Helen S. Ogilvie (the Scottish 

 samples). The latter scientist herseif has vvritten the chapter on the 

 Scottish investigations (p. 34 — 51). 



The paper consists of a special part (p. 12—51) and a general 

 part (p. 51 — 138). 



In the special part a description is given of the plankton 

 production of the different waters at the given time (May-June 1912). 

 It contains the following sections: The Bernholm Deep (Baltic); 

 the Danish Waters; Skager Rak, February; Skager Rak, 

 fune; the South western North Sea; sections across the North 

 Sea from Shields towards Lindesnes; sections from the Sogne 

 Fiord to the Norwegian Sea N. of the Faeroes; the Faeroe- 

 Shetland Channel; The Northern North Sea. 



The general part includes the two following sections: 



1. Remarks on the separate species (p. 52—113). All the species 

 of protophytes and protozoa found in the samples are enumerated, 

 arranged alphabetically within the main systematic groups. The 

 last number is 215. Under each species notes on its occurrence and 

 quantitative distribution etc. are given. These noles are rather com- 

 prehensive in regard to several of the more important and common 

 species, e. g. several Chaetoceras- and Rhisosolenias'^ecie's,, Lepto- 

 cylindrus, Nitsschiä delicatissimn, and especially the Ceratia, the 

 density and vertical distribution of which are discussed in detail. 

 Into this section some scattered morphological and biological obser- 

 vations have been put. Thus the auxospores of Chaetoceras, constric- 

 tutn are described and figured, further the restingspores of CA. s/j^m- 

 docrinitiirn and Leptocylindriis danictis which originale within the 

 auxospores. Here we also find three new species, viz. L. minhnns, 

 Exuviaella globosa and E. perforata described. 



2. The second section of the general part deals with the ge- 

 neral conditions of life of the plankton production 

 (p. 113—138) under three headings: A. The Variation of the quantity 

 of plankton according to the depth; B. Horizontal quantitative varia- 

 tions in the plankton; C. Seasonal Variation in the quantity of plankton. 



In a Short review it is impossible to sum up all the interesting 

 items dealt with in this part of the paper, it is necessary to refer 

 the reader to the paper itself. Some few points may be chosen: 



From his studies of the material worked out and from other 

 sources the author arrives "at the result that the light Optimum 

 for far the greater part, if not for all, of our assimilating plankton 

 algae is situated close to the surface, probably not as deep as 10 m., 

 and we might perhaps even venture the assertion that algae occur- 

 ring in our latitudes with maximum, deeper than 30 m. have never 

 any Optimum of development down there, but are in a relatively 

 stagnatino- period of life". 



As to the question of the influence of the coastal water on the 

 development ot the plankton the author uses the working hypothe- 

 sis, "that the great amount of plankton which occurs in the coastal 

 waters and from thence can spread far out in the sea, is first of 



