280 transactions liverpool biological society. 



Comparison of Bay with Sea. 



The question arises, to what extent do the tow- 

 nettings taken across Port Erin Bay give a correct 

 indication of the condition of the Plankton in the sea 

 outside? On examining our results from Stats. I and III, 

 and comparing with the records from the bay, we find as 

 follows : — 



The Total Plankton reaches a much higher level 

 in the sea outside about the middle of May ; but in June 

 and in August the numbers are higher in the bay. Still, 

 on the whole, the two curves follow the same course. 



The Diatoms show no appreciable difference when 

 those from outside are taken into account. 



The Dinoflagellata begin their summer increase 

 three weeks earlier in the sea outside, and in the middle 

 of May stand at a much higher level, but at the end of 

 May and in June, and also in August, they are consider- 

 ably lower outside than in the bay. The numbers for 

 Ceratium tripos are much higher throughout April 

 outside, reaching 15,900 in the weekly average as against 

 1,800 in the bay. But, on the other hand, by the end of 

 May the bay numbers have reached 21,000 as against 500 

 only outside. 



Oikopleura shows very little difference, but the vernal 

 maximum occurs rather earlier outside the bay. 



Sagitta seems to congregate in larger numbers in the 

 bay. It is there that all the larger hauls were made (up 

 to 2,100), while outside it never reaches 75 in a haul. 



Tomofteris (taking the three years into account) has 

 its maximum in the open sea in June and July, while 

 inside the bay it has a still higher maximum in October. 



The Copepoda agree fairly well in dates, but the 

 numbers per haul run larger in the bay. The largest 



