SEA-FISHERIES LABORATORY. 281 



hauls occur, however, in the autumn, when we have no 

 outside data for comparison. 



The Cladocera appear first outside the bay in 

 '07-'08, inside in '09; the maxima appear to correspond 

 fairly closely in point of time, though on the whole the 

 numbers run higher in the bay, and the catches remain 

 large for a longer time in the bay than outside. 



On the whole, the bay catches are richer per haul, 

 but in regard to the periods of occurrence of the various 

 organisms there does not seem to be any notable constant 

 difference. 



Annual Position or Chief Maxima. 



We have drawn curves for the three important 

 groups, Diatoms, Dinoflagellates and Copepoda, for each 

 of the three years separately, and have also superposed 

 the curves for the three years on one sheet in order to 

 determine whether the groups appear in succession in the 

 same order year after year. It is evident from what we 

 have already stated above that the maxima of the whole 

 plankton, and also of the component groups, are not 

 necessarily in the same months each year — the Diatom 

 vernal maximum, for example, may be in March ('07), 

 April ('09), or May ('08) — but still it is possible, of course, 

 that the relative positions may be retained, and that an 

 early or late season may affect all groups equally. 



Our curves show in '07 the Diatom maximum in 

 March, while the Dinoflagellate line showed a consider- 

 able rise in April and May, and a further higher peak in 

 July, and the Copepoda rise keeps about a month behind 

 the Dinoflagellates till June, when it runs up to its early 

 summer maximum, followed after a depression in August 

 by a still greater maximum in October. 



In '08 the Diatom maximum is in May, and the 



