Life of the Waters 377 



by a perforated cork covered with a circle of fine bolting 

 cloth. After the water has been concentrated to 1/50 or 

 1/100 part of its original volume, the cork is removed, the 

 sand washed and the washings, containing the organisms to 

 be counted, preserved. This method, like all others, has 

 its advantages and disadvantages, principally the latter, but 

 for general purposes is perhaps as little objectionable as any. 



But the biologist relies not alone upon devices of his own 

 cunning. In his search for the creatures of the sea he employs 

 the whale as a retriever and in its capacious maw finds stores 

 of undigested information. The most primitive, but withal 

 the most efficient plankton trap known, is the pharynx of 

 the ascidian or sea squirt, which is perforated by numerous 

 minute openings through which water is strained," the animals 

 and plants which it contains being retained in the pharynx to 

 serve as the animal 's food. By studying the stomach contents 

 of these forms much has been learned of the microscopic life 

 of the sea. 



In studies of fresh water life many appliances are used 

 similar to those employed for marine work, and but few of 

 a special type are required. The methods employed here are 

 necessarily simpler than those used in investigation of the 

 sea, with its profound depths, its mighty waves and powerful 

 currents. In work upon large bodies of fresh water however 

 such as our Great Lakes, conditions are found resembling in 

 many ways those of the sea, and here especially must the 

 methods and apparatus of the oceanographer be largely re- 

 sorted to. Such apparatus as is peculiar to fresh water 

 research is described in various technical and special works, 

 and does not call for special mention here. 



Fresh water studies in the United States, apart from those 

 of the most general character, have been prosecuted mainly 

 by the Massachusetts State Board of Health, and the water 

 works department of Boston, Mass., and Brooklyn, N. Y., 

 the U. S. Bureau of Fisheries, the Illinois State Laboratory 

 of Natural History and the Natural History and Geological 

 Survey of Wisconsin. The first two of these agencies ha.ve 

 studied the drinking waters of their respective communities 

 primarily from the sanitary standpoint; the Bureau of 

 Fisheries is interested primarily in the commercial utilization 

 of our aquatic resources, while the other institutions have 

 approached their problems from primarily the purely scien- 

 tific angle with secondary reference to the practical results. 



We are accustomed to think of the suitability of water for 

 drinking and general domestic purposes in terms of bacterial 

 and chemical character, overlooking the fact that there are 



