90 The Ohio Journal of Science [Vol. XX, No. 4, 



METHODS OF STUDY. 



Since the collections were made at or near the shore, a very 

 simple outfit sufficed. This included a pipette one foot long, 

 another very short one, a spoon for scraping algae from stones 

 and wood and lifting material from the bottom, a thermometer, 

 and tumblers. Several stations were selected, with the idea 

 of obtaining environments as varied as possible. These included 

 those parts of the water constantly shaded, those shaded only 

 a part of the day, water containing much decayed material, 

 algae and sediment in clear spring water, algae growing on 

 submerged wood, and those on submerged rocks. Sediment 

 was collected in water a foot or more deep and from leaves 

 submerged but a few inches. Floating as well as submerged 

 plant material was taken. The material was examined as soon 

 as possible after it was collected and then every few days for a 

 period of a month or more. When an animal appeared only 

 after the culture had been standing in the laboratory, this fact 

 is mentioned when the particular animal is discussed. Col- 

 lections were made once a week when possible, though this rule 

 could not always be adhered to, partly because of lack of suffi- 

 cient time, partly because of the weather. It will be 

 remembered that the winter of 1917-18 was an unusually severe 

 one. 



Reports on atmospheric temperature, degree of cloudiness, 

 and other weather conditions were obtained from an office of 

 the United States Weather Bureau, situated on a hill overlooking 

 Mirror Lake. Since the limited duration of the study made 

 impracticable any attempt to establish correlations between 

 the appearance or disappearance of various forms and the 

 weather conditions, only a brief summary of the latter will be 

 given. 



Relatively few clear days are recorded for the time between 

 October 1, 1917 and February 28, 1918. In March, the sky 

 was clear perhaps half the time. The precipitation was below 

 normal during most of the period; in October and January it 

 rose somewhat above the normal for this region. The tem- 

 perature showed a pretty steady fall until early in December, 

 when the mean daily temperature went below zero Fahrenheit 

 for the first time. Exceptionally severe weather continued 

 throughout December, January, and the first part of February. 



