170 
president’s address. 
In Lake Constance it is said that the diatom Cyrnutoplcura 
solca (Brebisson) occurs at a depth of 160 and 240 m. ; this 
is a common species, and is in our Norfolk list. 
The greatest depth at which a green plant has been found 
is 60 m.. at which great depth Forel found a moss Thamnium 
lemani (Schnetzler) flourishing at Y voire, on the Lake of 
Geneva. Animal life is far more numerous than plant life 
in the abyssal region, and Forel enumerates no less than 
79 species, either erratic or permanently located, down to 
a depth of no m. ; of these, 14 species are vertebrates. 
Those organisms which make their home in deep water 
are specially adapted to their environment, and are usually 
smaller, paler, and feebler than their allies of shallow water. 
In some cases ( e.g ., Fredericella) species, which in shallow 
water are fixed, live free upon the mud of deep water. The 
animal life of this region subsists upon the organic debris 
which finds its way downwards from the regions above. The 
pelagic fauna and flora, especially the more minute forms 
which compose the plankton or floating association, has been 
very carefully studied in Germany by Apstein and Zacharias, 
among others, and a large part of the work of the fresh water 
station at Plon has been occupied with such researches. 
The methods devised by Hensen for the study of marine 
plankton have been imported into lacustrine work, and 
a great deal of exact information has been collected upon 
the qualitative and quantitative distribution. 
Most elaborate methods are used, both in making the 
collections and in counting the results, and this has been done 
not only in one lake, but in several, and at all seasons of the 
year ; so that a good idea of the seasonal and geographical 
distribution has been obtained. 
To show the detail into which this subject has been pursued, 
I show on the table a tabulated statement by Apstein of 
the number of organisms of different species found under 
