SEA-FISHERIES laboratory. 199 



results of hauls showing special features of the plankton 

 at different times of the year. 



Form ]^o. 10, representing the hauls taken on an 

 off-shore station, on April 5th, shows the condition of 

 affairs during the spring maximum of Diatoms. It will 

 be noticed that 14 millions of one species, Chaetoceros 

 contortum, were present in one haul of the Nansen net. 

 The total number of Diatoms in that haul was nearly 

 IT millions, including two millions of Thalassiosira 

 nordenshioldii. 



Comparatively few Copepoda and other large organisms 

 were present. It will be noticed that 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. They may represent, apparently, some- 

 thing like double or half the quantity of organisms 

 obtained in neighbouring hauls. 



For comparison with Form 10 we print Form 71, 

 showing a similar series of hauls taken late in August 

 from a neighbouring station. Here there are practically 

 no Diatoms present, there being only a very few 

 individuals of Biddidphia mohiliensis. On the other 

 hand, the Copepoda are more abundant than they 

 were in April. For example, compare Oitlwna similis, 

 where only tens, amounting at most to a few hundreds, 

 were present in April, and thousands (reaching eleven 

 thousand in the weighted net) were in the August haul. 

 Other interesting differences will be noticed on comparing 

 the two Forms. 



