[mMcmuRRICH] PLANKTON OF BRITISH COLUMBIA COAST 89 
of winds and currents, an approach to a monotonic condition being 
indication possibly of a reproductive rhythm such as that which pro- 
duces the vernal maximum of plankton protophytes. 
The similarity of the planktonic constituents of British Columbian 
waters to those of the North Atlantic is very striking, the great majori- 
ty of the forms being specifically identical with those occurring in 
the latter area. This is probably to be explained on the basis of a 
circumpolar distribution of the majority of the forms concerned, 
although the possibility should not be neglected that in the case of 
some forms the similarity may be due to a former circumpolar dis- 
tribution under different climatic conditions. In other words, it 
is possible that certain forms may occur upon both the eastern and 
western coasts of Canada, between certain latitudes, and not on the 
intervening northern coasts, being isolated detachments of species 
which in earlier times possessed a circumpolar distribution. There 
are some indications that such a condition occurs, but until a thorough 
knowledge of the zoology of our arctic waters is obtained, they can 
be regarded only as pointing to a possibility. 
