264 iA, BATHER [ocroBER 
expedition,’ and the writings of many other Scandinavian naturalists, 
trench more or less upon the region herein considered. Dr. Loénnberg 
also admits that his time and means have both been limited. He 
had only a little sailing-boat, with dredge and trawl no bigger than 
could be worked by hand. ‘These facts add to the suggestiveness of 
his results. For, if he has been able, with such feeble opportunity, 
to add to the list, not merely of the Swedish marine fauna, but of 
forms new to science; if his work already enables him to foreshadow 
conclusions of scientific no less than practical interest, then it is clear 
that there is room for continued and still more detailed investigation. 
Considering the fluctuations in the number and kinds of fish that are said 
to have taken place in the Sound during this century, the mere list of » 
captures has a certain value for comparison with past and future 
lists. Indeed the only previous list is that which Oersted pub- 
lished so long ago as 1844, in his little book “De regionibus 
marinis.” 
In a short introduction Dr. Lonnberg discusses the conditions 
governing the distribution of life in such a region as Oresund. The 
changes of wind and of current, which so frequently take place, may 
in a day or two completely alter the composition of the minute surface 
fauna, and thus induce a corresponding migration of such pelagic fish 
as herring and mackerel, which feed on these idly drifting organisms. 
To be of practical value, the study of such changes must continue 
from day to day. It is otherwise with the sedentary or slowly moving 
life of the bottom, and with the fish that feed thereon, such as cod 
and flat-fish. The constituents of this fauna, abiding in the same 
place from year to year, must be suited to the conditions there obtain- 
ing, and must be able to survive all those changes in salinity, tem- 
perature, and the like that may occur in the various seasons. Slow 
geological changes may have caused the fauna to alter slightly from 
its original composition, and may have eliminated some of its earlier 
elements ; but their effect is more likely to be seen in a less favourable 
development of individuals. Experiment and observation have shown 
that many marine species can accommodate themselves to a slow 
reduction of salinity, or other change in the chemical composition of 
the water, although they may show signs of the change in their smaller 
size or less calcified skeletons. A difference of depth is not so im- 
portant, and in any case since the so-called Zzttorina-age, which in 
the Baltic area was the immediate forerunner of present conditions, 
the amount of shallowing has not exceeded 5 metres. This, on the 
data generally accepted, and assuming a regularity in the change, 
implies a lessening in depth not more than 5 centimetres a century. 
It follows from the arguments here briefly outlined that past 
fluctuations in, and the present distribution of, what one may call 
the edible fauna, with all their practical effect on the human neigh- 
bours, may be best interpreted by a detailed study of the present fauna, 
