134 SUMMAKY OF CUEKENT RESEARCHES RELATING TO 



Changes in Life-conditions in Illinois River. — S. A. Forbes and 

 E. E. Richardson {Bull. Nat. Hist. Survey, Illinois, 1919, 13, 139- 

 56). A study of the changes in the plankton and fishes in the Illinois 

 River since the increase of Chicago sewage emptied into the stream 

 and the reclamation of parts of the overflow regions. " A river and its 

 plankton are a flowing soil and its crop, both slipping away continuously, 

 but both renewed constantly from an exhanstless source of supply. 

 The fertility of the flowing water at any time is not dependent on the 

 fertility of that which has preceded it, but on materials of fertility 

 brought into it from the watershed .... The plankton productivity 

 of the stream does not depend primarily on the richness and extent of 

 its own flowing waters, but on those of its subsidiary breeding grounds, 

 and if these are not adequate to the maintenance of a plankton sufficient 

 to consume all the readily available food materials of the stream, more 

 or less fertility of the current waters must go to waste." The yield of 

 fishes in the Illinois River has been diminishing for many years in the 

 face of a greatly increased and rapidly growing supply of the raw 

 materials of their food, because of the narrowing, of the backwaters, 

 which are for the river important places of digestion and assimilation 

 in which the organic wastes of the city and of the land are worked up 

 into forms fit for food for .the higher animals. It is not only space but 

 time that has been seriously reduced. J. A. T. 



Monthly Occurrence of Pelagic Eggs in Port Erin Bay in 1918. — 



A. Scott {Lancashire Sea-Fisheries Laboratory Report, 1919, 27, 15- 

 24). It was found that pelagic eggs were present in the plankton for 

 nine months out of the twelve. The increase at the beginning of the 

 year was very rapid, rising from 0*83 per haul of the coarse net in 

 January to 106 '4 in March — the maximum. A reduction set in during 

 April, which was continued to June. A well-defined increase took 

 place in July, which was largely due to the presence of the eggs of 

 two Species of fish (rockling and topknot). After that the pelagic 

 ■eggs ceased to be conspicuous among the plankton organisms, and 

 finally disappeared in September. J. A. T. 



Intensive Study of Isle of Man Plankton. — W. A. Herdman, A. 

 Scott, and H. M. Lewis {Lancashire Sea- Fisheries Laboratory Report, 

 191^, 27, 25-35). " One conclusion that is becoming clear from our 

 accumulated observations of the last ten years is the surprisingly small 

 number of different kinds of organisms — both plants and animals — 

 that make up the bulk of the plankton that is of real importance in 

 relation to fish. Our food from the sea seems to depend, in great 

 measure, ultimately upon comparatively few species of Diatoms and 

 Oopepoda respectively. A very large proportion of the Diatoms in the 

 spring plankton and of Copepoda in that of late summer belong in 

 ■each case to a very few different kinds, so that one can select about half- 

 a-dozen species of Copepoda which constitute by far the greater part 

 of the summer zooplankton, and about the same number of Diatoms 

 which similarly make up the bulk of the spring phytoplankton year 

 after year. These few species, belonging to these two very widely 



