136 PLANKTON OF WISCONSIN LAKES 



water on August 11, to a maximum of 768,000 per liter on October 23. 

 Cryptomonas reached a maximum of about 65,000 per liter on the latter 

 date, while the same maximum was noted for the disc-shaped flagellate 

 on August 11. Aphanocapsa delicatissima yielded a maximum of 444,- 

 000 colonies per liter on August 11, while another blue-green alga, 

 Oscillatoria, rose to 477,500 per liter on October 23. In fifteen other 

 forms of algae, exclusive of the diatoms, the numbers varied from 2,000 

 to 75,000 per liter of water. The diatom Melosira numbered 307,000 

 filaments per liter on October 2, while Stephanodiscus rose to 20,000 

 per liter on this date. 



In the series of catches obtained in 1916, Chlorochromonas showed 

 two maxima ; the first one was noted on June 25 when the number rose 

 to 665,500 per liter and a second maximum of 512,000 was found on 

 September 7. The minimum number for the entire series of catches 

 collected in this year was found on July 25, namely, 10,000 per liter. 

 The maximum for the disc-shaped flagellate was 204,000 per liter on 

 September 7. Seven other forms of protozoa were noted from time to 

 time, but none of them appeared regularly in the various catches ; the 

 most abundant one was Cryptomonas, of which 105,000 individuals per 

 liter were found on October 2. 



Aphanocapsa delicatissima gave a maximum of 512,000 per liter on 

 October 2, while the maximum for Oscillatoria was 768,000 per liter on 

 August 23. It may be noted here that Oscillatoria was found in con- 

 siderable abundance both in Lake Monona and in Lake Waubesa, but 

 it was not present in any of the centrifuge material from Lake Mendota. 

 Small colonies of Microcystis were present in all of the nannoplankton 

 collected in Lake "Waubesa after the middle of July; they numbered 

 205,000 per liter in both of the August samples in 1916. With the ex- 

 ception of the first sample (No. 632) portions of the filaments of Ana- 

 baena were more or less abundant in all of the catches of this year; 

 the number ranged from a minimum of 3,400 per liter to a maximum of 

 410,000 per liter, the latter number being noted on September 7. Four- 

 teen other forms of algae, exclusive of the diatoms, were found in the 

 various catches, but all of them were irregular in their appearance; 

 their numbers varied from about 1,000 to 102,000 per liter of water. 



The most important diatom was Melosira; it was present in all of 

 the catches obtained after the middle of July. The largest number, 

 375,000 per liter, was noted on September 19. Half a dozen other dia- 

 toms were found in the material but they did not appear regularly in 

 the various catches ; of these forms Stephanodiscus, Coscinodiscus, and 

 Coceoneis were obtained most frequently. 



Only one form, Aphanocapsa, gave a maximum number on October 2 

 when the largest quantity of organic matter was obtained in the cen- 



