SEA-FISHERIES LABORATORY. 997 
July Aug. Sept. Oct. Nov. Dec. 
Se LOUAL OA VS WOLKOd om cacecased 9 9 9 9 8 9 
-3 Total number of species ...... 20 17 21 22 21 26 
S sé occurrences... 135 O87 1264 4145, 116 4,127 
& Mean occurrence ............... Gib beiG7, G 6-59 5-52 4-88 
Percentage of possible ......... 75 64 66-6 73:2 69 54-2 
= Total number of species ...... 19 15 28 28 23 20 
es 4 occurrences... 72 Soe LOL Lie 90 
% Mean occurrence ............... 3°79 4:2 4:25 5-75 4.87 4-5 
AZ Percentage of possible ......... 42-1 46:6 47-2 63:9 60:9 50 

On comparing the figures with those for 1909 
(Part III, p. 255) we find a close agreement in the 
character of the months, there being only one out of the 
twelve which differs. August is this year more oceanic 
(as it was in 1907), while in the two intermediate years 
it was more neritic. Irom the tables for the four years 
now before us we can say that mid-winter (December 
and January) and mid-summer (July) are more oceanic 
in all cases, while the intervening months, and especially 
April and May and October, are in all four years neritic 
in character. 
SUNSHINE AND PHYTO-PLANKTON. 
It is quite possible that Sir John Murray’s original 
suggestion, that the great vernal maximum of phyto- 
plankton—perhaps the greatest and most important of 

biological phenomena in the sea—is simply the result 
of the increasing amount of sunlight in the early 
months of the year, may eventually turn out to be the 
correct explanation. In the meantime there are several 
other possible causes that have been suggested, such as’ 
Brandt’s hypothesis that the fluctuations in the phyto- 
plankton depend upon the accumulation and_ the 
exhaustion of necessary inorganic food-matters in the 
water, perhaps the silica required for the shells of the 
U 
