78 



The relation of the dissolved gases of the water to the amount and consti- 

 tution of the life therein contained is an important problem, and an attempt 

 to collect data has been made in connection with the chemical survey of the 

 waters of the State. In July, 181)7, Prof. A. W. Palmer, Director of this 

 Survey, visited the station and made a number of analyses of the oxygen 

 dissolved in the surface and bottom waters in the lakes and river. In 

 1898 this was repeated, with Mr. R. W. Stark, assistant on the survey, 

 and a number of similar analyses were made, the carbon dioxide being 

 also determined. A series of collections extending throughout twentj'- 

 four hours was made from the surface and bottom waters of the Illinois 

 river with a view of determining the diurnal fluctuation in the amount of the 

 dissolved gases. In all these operations parallel collections of the plankton 

 have been made a,t the same time and from water collected in the same man- 

 ner, the plankton pump being used for the collection both of the plankton 

 and the water for gas analysis. The twenty-four-hour series collected in 1898 

 can be brought into correlation with the movements of the water-bloom, which 

 is a marked feature of the plankton of the river during the warmer months of 

 the year. About one hundred bottles are comprised in the collections belong- 

 ing in this series. 



The serial plankton work rests upon the supposition that a single catch 

 made in a typical locality of a lake or river will give a fair sample of the 

 microscopic life of the water, both as to its quantity and constituent organ- 

 isms. With a view to testing the validitj- of this supposition, Thompson's, 

 Quiver, and Mantanzas lakes and the river have in previous years been sub- 

 ject to extended examinations, collections being made on the same date at a 

 considerable number of localities at regular inifervals throughout the body of 

 water examined. In 1897 Thompson's lake was re-examined on this plan and 

 a biological ci-oss-section of the river was made at Havana. This series of 

 collections has been increased by twenty-five bottles duriugthe period covei'ed 

 by this report. 



The tests looking towai'd the detection and con-ection of sources of error in 

 the plankton method and the justification of changes in it which we have 

 made, have been continued during the past two years. Of the collections 

 made in these tests about one hundred and fifty have been preserved. Tests 

 have been made of the errors i-esulting from leakage, from the progressive 

 clogging of the drawn net and the consequent variable coefficient, and from 

 the active escape of the larger organisms of the plankton. Several types of 

 funnels for the in-take of the plankton pump have also been devised and 

 tested. Tests of the leakage through the silk and efforts to correct it by some 

 form of micro- filter or precipitation method have also been continued. A 

 variety of filters have been examined, including the Sedgwick-Rafter sand 

 filter, using sharp Berkshire sand according to the directions of Calkins *, 

 Jackson t, and Whipple t. The loss by leakage from this filter was so great 

 that we abandoned it and have boeu using filter paper as a supplementarj* 

 method of collection since September, 1890, in all regular plankton examina- 

 tions. For a short time ordinarj' filter paper was used, but owing to the 

 looseness of its textui'e and consequent entanglement of the plankton and 

 shedding of lint we rejected this pap;>r and have since used the "hardened 

 filter paper,'' No. 575, Schleicher & SchuU. The water from which the sample 

 for filtration is taken has been obtained by means of the pump. It was- often 

 necessary to take a much larger amount than was used for filtration in order 

 to secure a vertical collection. To obviate this ami also to secui-e greater ac- 

 curacy in the oallection of a vertical sample, a vertical water-trap was de- 

 vised, which consists of a light brass tube three inches in diameter and eight 

 feet long, at whose lower end is a sliding brass gate by which the bottom of 

 the tube can be closed after it is lowered to the desired depth. 



Although the fiiter-paper collections served to correct the loss by leakage in 



♦Calkins, G. N.— The Microscopical Examination of Water. Rep. Mass. State Board of 

 Health. 18!U, pp. 3!p6-121. 2 folding tables. 



t.Iackson. I). I").— An improvement in the Sedgwick-Rafter Method for the Microscopical 

 Examination of Water. Tech. Quart, Vol, ix, pp. 271-274. 18%. 



tWhipple. G. C— Experience with the Sedcrwick-Rafter Method at the Biological Labor- 

 atory of the Boston Water Works. Ibid., pp. 275-279. 18%. 



