LINNB^Jf SOCIETY OF LONDON. 25 



day reached an average of 51 c.c. per haul. Other lesser elevations 

 are seen in June with 20 c.c, and August with 25 c.c. The catch 

 in some individual hauls runs a great deal higher than these 

 averages, the top score being the Nansen net on April 4th, with 

 164-5 c.c. Fig. 4, showing the average haul of plankton per 



Fig. 4. — Diagram showing average ]iaul of Plankton per month. 



Jan. Ftir War A^' Ma^ Jone J^lu A^J 5e|it- (Pet Nov. Dec 



month, brings out the great range and remarkable diversity 

 between adjacent months. 



The spring maximum in the amount of the plankton is clearly 

 due to a great and sudden increase in the amount of Diatoms 

 present (see fig. 3). The other rises seen later in the year, as in 

 June, August, and to a slighter extent in October, are less marked, 

 and are less clearly due to one cause. 



The hauls taken on an ofF-shore station, on April 5th, show the 

 condition of affairs during the spring maximum of the Diatoms, 

 when 14 millions of one species, Chcetoceros contortum, were present 

 in one haul of the Nansen net. The total number of Diatoms in 

 that haul was nearly 17 millions, including ' two millions of 

 Thalassiosira Nordenshioldii. Comparatively few Copepoda and 

 other organisms were present. The two surface gatherings of this 

 date were moderately alike, the same organisms were present in 

 both, although one net had, in some cases, about twice as many as 

 the other ; but still the hauls were of the same general type and 

 the quantities were, in most cases, not very different, showing that 

 one can get a good general idea of the fauna by such hauls, but 

 that one cannot depend upon their being minutely representative. 



