582 



INDEX. 



Plankton — Continued. 

 enumerative or counting method 



of determining, 2 1. 

 gravimetric method of determin- 

 ing, 18. 

 and volumetric method of de- 

 determining, combined, 18. 

 oblique-haul method of collect- 

 ing, difficulties en- 

 countered in, 11. 

 operation of, 2, 10. 

 preservation and examination of, 



17-21. 

 pumping method of collecting, 

 2, 12-17. 

 advantages of, 17. 

 operation of, 16. 

 quantitative examination of, 18. 

 settling and centrifugal methods 

 of volumetric determination of, 

 ig, 20. 

 Studies. I. Methods and Ap- 

 paratus in Use in Plank- 

 ton Investigations at the 

 Biological Experiment 

 Station of the University 

 of Illinois, 1-25. 

 bibliography in, 22-23. 

 explanation of plates in, 23 



25- 

 Studies. II. On Pleodorina illinoi- 

 sensis, a New Species from 

 the Plankton of the Illinois 

 River, 273-293. 

 bibliography in, 291-292. 

 explanation of plates in, 293. 

 Studies. III. On Platydorina, a 

 New Genus of the Family 

 Volvocidae, f ro m the 

 Plankton of the Illinois 

 River, 419-440. 

 explanation of plate in, 440. 

 literature cited in, 437. 

 variations in, at Havana, 111., 

 11. 



Plankton — Continued. 



vertical-haul method of collect- 

 ing, 2. 

 inapplicable in Station 

 waters at Havana, 111., 



3- 



work on the Illinois River and 

 Adjacent waters, scope of, 1. 

 Planorbis, Opercularia nutans 



found on, 340. 

 Plate, Ludwig, Beitnige xur Xatur- 

 geschichte der Rotatorien, 

 cited, 367. 

 on Brachionus bidens, 381. 

 on Triarthra terminalis, 367. 

 Platydorina, 436, 437. 

 A new Genus of the Family Vol- 

 vocidae from the Plankton of 

 the Illinois River, article on, 

 419-440. 

 associates of, 420 i 42i. 

 caudata, 419, 437. 



arrangement of cells of, 426. 

 characteristic features of col- 

 ony of, 423. 

 description of, 421-435. 

 parasite of, 425, 434. 

 size of colony of, 422,425. 

 specific characters of, 435. 

 type of cells of, 425, 427. 

 colors of, 422. 



discussion of term colony as ap- 

 plied to, 433. 

 explanation of plate in Kofoid's 



article on, 440. 

 generic characters of, 435. 

 literature cited in Kofoid's arti- 

 cle on, 439. 

 locomotion of, 430. 

 systematic position and relation- 

 ships of, 433. 

 reproduction of, 432. 

 platyptera euryptera, Polyarthra, 



367- 

 Polyarthra, 340, 352,354, 355,367. 



