ANNUAL DISTRIBUTION OF THE ORGANISMS. 45 



When one examines this table, the degree of uniformity in 

 successive years is somwhat surprising, for we must expect an- 

 nual variations in the maxima of the total plankton. I have 

 already called attention to the fact that all the collections of 

 1900 were larger than those of 1902. This was especially 

 marked in the case of Birch, Stone, and Sand lakes, and was 

 largely due in each case to the greater number of Crustacea, es- 

 pecially of the Diaptomi; in Sand lake there was also a larger 

 number of the algae in 1900, but it was in the Crustacea that 

 there was the greatest difference. 



The large collection in Shamrock in 1902 was due in the 

 main to the comparatively large number of Daphnia pulicaria; 

 the great size of this form makes it, when present, an impor- 

 tant factor in the total plankton. 



In the distinctively shallow lakes, Eagle, Pelican, and 

 Shawano, the uniformity in the successive years was very 

 marked, the differences being hardly greater than might be ex- 

 pected from hauls made on successive days in the same year. It 

 will be noticed that the uniformity in the case of the shallow 

 lakes is much greater than in the deep lakes. 



In comparing the lakes with each other at each period of col- 

 lection we find that Pelican has the greatest amount of plank- 

 ton in the last three years, but was outranked by Sand lake in 

 1899. This large amount of plankton in Sand lake in 1899 

 was due to the abundance of "bloom," in which the most 

 prominent plant was Anabaena. I think this is an exceptional 

 record for Anabaena for, as I have stated before, the plants of 

 the bloom flourish especially in warm weather, and we should 

 not expect them late in September. The time of the collection, 

 too, had been preceded by cold weather, and on the day of the- 

 collection ice had formed by the roadside in the morning. 



Eagle lake was a constant second to Pelican in the years un- 

 der examination. In regard to the other lakes there seems to 

 be no fixed order of precedence. 



In comparing the years 1900 and 1901 it is interesting that 



