264 F. A. BATHER [octobee 



expedition," and the writings of many other Scandinavian naturalists, 

 trench more or less upon the region herein considered. Dr. Lonnberg 

 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 Littorina-a,gQ, 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, 



