Aigae. <>71 



cauda. Species of Cyanophyceae occur more frequently in the 

 lower than in the higher parts of the river. No Peridiniaceae 

 were observed. A table is given in which are enumerated 

 Kfty-four species and five varieties, together with their distri- 

 bution and the relative number of individuals found. The 

 samples were collected from a rowing-boat by means of a 

 funnel-shaped net of fine gauze, having the lower narrow end 

 attached to a glass tube. Ethel S. Gepp (nee Barton). 



GRAN, H. H, Das Plankton des Norwegischen Nord- 

 meeres von biologischen und hydrographischen 

 Gesichtspunkten behandelt. (Report on Norwegian 

 Fishery- and Marine - Investigations. Vol. II. Bergen 1902. 

 No. 5. 222 pp. With 1 plate and K> figures in the text.) 



C.hapter I (p. 1 — 10) is an introduction on the principies of the 

 marine plankton-investigations 



Chapt. II (p. 11 — 70) contains the biology and biography of some 

 irnportant plankton-species: 1. Halosphaera viridis Schmitz occurs in the 

 Norwegian Sea from August to May ; during the first months the cells 

 are small („Halosphaera minor Ostf."), but increase by and by until in 

 April-May they throw off the outer membrane while the inner one dilates 

 considerably ; then the cells disappear suddenly, and it is to be suppo- 

 sed that zoospores hav r e been produced. It is an oceanic, holoplanktonic 

 species which in the Norwegian Sea has been found only in the eastern 

 part following the warm current. 2. Phacocystis Ponchetii (Hariot) 

 Lagerh. is a neritic species, occuring mostly near the coasts and only 

 during a short time every year ; it then forms the main part of the 

 plankton. 3. Diatoms. The author describes a curious sporulation in 

 Rhizosoleiiia styliformis. In some samples, consisting partly of this 

 species, several specimens were found which contained more or less 

 uumerous small nuclei ; the number was always a multiplum of 2 and 

 the highest number observed was 128. The cells with the numerous 

 nuclei were the smallest specimens in the samples. In the same samples 

 also the hitherto unknown auxospores of the species occur, and the 

 author supposes that the small nuclei should be male-gametes which 

 fecundate other cells, these again producing the auxospores — a quite 

 oew form of reprodution among diaioms. — With regard to the distri- 

 bution 5 species of Chaetoceras and 3 species of Thalassiosira are dis- 

 cussed as neritic types and 9 species of difierent genera as oceanic 

 types, of the last especially Rhizosolcnia styliformis is irnpor- 

 tant \. Peridinea are the littest organisms for the study of the 

 occan-currents ; most of thetn are oceanic species which belong to 

 4 groups, viz. arctic, boreal, temperate-atlantic, and sub- 

 iropical-atlantic. As types of the groups 4 closely allied forms of 

 itium macroceros s. 1. are discussed. In this discussion the author 

 uses the Galton-curve in making out the relations between C. arcticum 

 and C. longipes; it is for the first time this method has been used in 

 planktology. 5. Copepods, Ostracods and Cladocera are of 

 great importance in the plankton, but must be omitted in this abstract 

 as not belonging to the phytoplankton. The author has studied the 

 commonest Copepod Calanus finmarchicus , thoroughly and with very 

 interesting results. 



Chapt III (p. 71 106), „Plankton and H y d r ogra p hy", gives 

 interesting reflections about the relations between plankton and hydro- 

 graphy. 1. The Classification of the plankton-organisms is of two kinds, 

 viz: Classification after p 1 a n k t o n-a s so c i a ti o n s and Classification 

 after plankton-elements. A plankton-element contains the organisms 

 which have about the same biographical distribution, while a plankton- 



