1160 Proceedings of Royal Society of Edinburgh. [sess. 
kills, and that some of those forms tohich, according to their primeval 
structure , were best adapted to plankton-life, are now in fact, under 
the new conditions, about to develop processes. 
I have of course meant that the adaptation has been going on for 
immense spaces of time, and is going on to this day ; that many 
of the Desmids have existed under these pelagic conditions for a 
great length of time is a matter of course which I did not think 
necessary to point out especially, and which I never have denied. 
On the other hand, I suppose that the authors will hardly deny that 
the adaptation continually takes place up to this very day ; so that 
also on this point the suppositions of the authors are not 
at variance with mine. Besides, the very thorough study of the 
plankton Desmids by the English authors has greatly augmented 
our knowledge of the extremely interesting subject : the plankton 
Desmids of the Scottish and probably also the Icelandic loch? ; 
all in all, I cannot hut see that they support the correctness of my 
suppositions set forth on p. 431. I am fully convinced that it is 
an exaggeration to say (Messrs West, p. 477) that the lochs of the 
west and north-west of Scotland were probably richer as regards the 
phytoplankton than any lakes previously examined, and it is not in 
accordance with facts that the Danish plankton is relatively much 
poorer in Chlorophyceae, especially Conjugates (Messrs West, p. 514). 
Only with regard to the Desmids these two sentences are fully 
correct. The plankton in the lakes of the northern part of the 
Central European plain is much richer with regard to the 
number of species as well as to the masses in which the species 
appear. Especially with regard to Chlorophycese our plankton flora, 
the Desmids always excepted, is much richer than the Scottish lakes. 
As my knowledge of the Scottish lakes of course could only he 
very furtive, I have in my paper only set forth the results of the 
explorations as mere suppositions. Several of those suppositions, 
viz., the relatively small quantity of plankton, the slight perio- 
dicity, the slight seasonal variations, the absence of well-marked 
maximum development of Diatoms, the scarceness of Myxophycese, 
especially Oscillatoria, Lyngbya, the English authors now regard 
as a “summary” of our knowledge of the phytoplankton. This 
may he so ; still, I feel inclined to pronounce that in my opinion 
the two authors have by no means grounded these suppositions 
