Aq 2 BOTANICAL GAZETTE [JUNE 
pletely launched and set under way. (4) We must study great Saves of 
individuals and employ statistical methods of comparison. (5) The doctrine 
of discontinuous evolution is now clearly before us. (6) We are Spee 
find a pathway through the bewildering maze of hybridization.’’—J. M. C 
River plankton. 
INa eae of the Illinois State Laboratory of Natural History,3 a bulky 
volume of something over five hundred pages, we have by far the most 
cele ees yet made to the subject of potamoplankton. There 
ve been many extended series of observations on the plankton of lakes, but 
river plankton has received very little attention. This has been partly 
because of the greater richness of limnoplankton, partly because the prob- 
lems of limnoplankton are simpler than those of potamoplankton, and per- 
haps of greater interest, and partly, doubtless, because the lakes are more 
important for the production of fish. The greater credit, perhaps, ought to 
be given for the attempt to throw light on the problems of river plankton by 
ee continued systematic observations. 
ork centered at Havana on the Illinois River, and collections were 
Sia not only in the river, but in neighboring waters, including Spoon 
River, Quiver Lake, Dogfish Lake, Flag Lake, Thompson’s Lake, and Phelps 
Lake. The conditions in the Illinois River are unusual because of the large 
amount of sewage that comes from Chicago and the other cities in its course. 
Spoon River is a typical prairie river with no artificial conditions. ‘The lakes 
examined are all connected with the river at the time of high water, and 
some of them have a permanent connection through the year. Thus the 
work of investigation included a study of the Illinois River, of a river ee 
taminated with sewage, and of several shallow bodies of water which were 
filled by overflow from the river and were stagnant for a greater or less os 
of the year. Something over a hundred pages are devoted to a somewhat 
detailed discussion of the geological and hydrographical features of the basin 
of the Illinois. : 
The remainder of the work is a discussion of the quantitative investiga- 
tion of the plankton. The methods of collection worked out by Dr. Kofoid 
are somewhat different from those employed at other stations, and the author 
naturally considers them superior. It may be questioned, however, whether 
the methods used in the shallow silt-laden waters of the river could be used 
with advantage in a study of limnoplankton. The centrifuge was used to get 
the plankton into compact form for measurement, and this method seems to 
be the most practical that has yet been devised. 
The study of plankton production was carried out with the most pains- 
3 Kororp, C. A., The plankton of the Illinois one 1894-1899, with introducto 
notes upon the hydiouraphy of the Illinois River and its basin. Part I. Quantitative 
investigations and general results. Bull. Ills. State a Nat. Hist. vol. 6. 8vo. 
xviii + 629. pls. 50, 1903 
