MARINE BIOLOGICAL STATION AT PORT ERIN. 



43 



particular occasion ; but we may aim at being able to 

 make, with a reasonable approximation to the truth, such 

 statements as : There are about ten times as many Diatoms 

 in a special part of the Irish Sea now as there were last 

 week, and in round numbers twice as many as at the 

 corresponding period of last year. 



With the object of formulating such views as to the 

 nature of the Plankton at any particular time, and as to 



Fig. 16. — Plankton nets drying after an expedition on S.Y. " Ladybird " 

 at Port Erin. (Photo by Edwin Thompson). 



the changes, both diurnal and seasonal, and the deter- 

 mining factors of such changes, we must endeavour to 

 make quantitative catches as accurately and as frequently 

 as possible, so that our samples may be as nearly represen- 

 tative and as nearly comparable one with another as the 

 difficult conditions will admit. These catches should be 

 made with standard nets, should be preserved and 

 measured according to a uniform system, and may then be 

 compared in bulk; but, in addition, the more important 



