THE BEHAVIOR OP CERTAIN MICRO-ORGANISMS IN BRINE. 55 



to contain, besides the Artemias, the two species of Dunaliella above referred to. The 

 movements of these unicellular, more or less pear-shaped algse by sweeps of their long 

 paired flagella, through the sirupy brine, were curiously slow and, apparently, deliberate. 

 There was none of the familiar swift jerky movement which one sees ordinary zoospores 

 executing under a microscope. 



The next examination was on November 7, 1906, after the first rain of the season. 

 The maximum specific gravity on this date had fallen to 1.190. This was both because 

 of the rain and also because brine had been pumped in from the so-called "pickle-pond." 

 In the "pickle-pond" the preliminary concentration occurs, in the course of which the 

 volume of liquid is greatly reduced and much calcium is thrown down. In this brine of 

 lowered specific gravity I saw fewer Artemias than nearly two weeks before, and the brine 

 had a slightly greenish tinge on the surface. This latter fact was accounted for by the 

 superintendent of the works as due to the rain. 



At this time, also, I collected the "mother-liquor" from the saltern from which salt 

 was being harvested. This "mother-liquor" had a specific gravity of 1.225. Its composi- 

 tion, though still a solution saturated with common salt (NaCl), had changed greatly in 

 its proportions. The ratio between the magnesium salts in the solution and the sodium 

 salts had changed to the extent of the salt precipitation. What the ratios of these mag- 

 nesium salts are to the calcium, sodium, potassium and other salts in the brines will 

 be shown later (p. 67) ; but I wish here to call attention not only to the concentration, 

 but also to the extraordinary composition of the solutions in these salt ponds. Despite 

 this remarkable concentration and composition, the two species of Dunaliella were present 

 even in the "mother-liquor," though in considerably smaller numbers than before. As 

 we shall see, these brines offer very striking exceptions to the rule implied by the idea of 

 "balanced solutions;" but as the brine organisms are living in concentrations ordinarily 

 regarded as fatal, they may be supposed to have adjusted themselves to the extraordinary 

 composition also. This whole matter, however, we shall understand better if, before 

 considering the composition of the solution, we first study the behavior of the organisms 

 during the progress of the seasons and in relation to the changing concentrations of the 

 solutions. 



Regular collections and examinations of the brines at Redwood City were begun in 

 January 1908. From the middle of January until the end of April collections were made 

 weekly, the specific gravities ranging during this time from Bay water at 1.023 to 1.165 

 in one of the salterns. The collections were all made at about 10 a.m., and were uni- 

 formly less productive of plants than those made at the afternoon hour adhered to from 

 January 1910 until June 1912. The relation of light to the position and distribution of 

 ciliate motile unicellular algse is well known, and the behavior of these markedly photo- 

 tactic brine algse is entirely similar. Thus my records show that during the winter and 

 spring of 1908 algse were found only in small numbers in the bottles of brine brought by 

 me to the laboratory from the various salterns. The reason for this, I believe, was that they 

 became fairly uniformly distributed throughout the brine during the hours of darkness 

 after collecting nearer and nearer the surface during the hours of daylight. Their maximum 

 concentration at the surface was generally in mid-afternoon, and the time of the collections 

 from January 1910 on was about 4 p.m. As these later records show, the algaa were 

 abundant, other things being equal, in the latter part of the day, when light had been 

 falling for hours upon the brine. Phototaxis, exhibited by these brine algse in bottle and 

 test-tube in the laboratory, is displayed, therefore, on a huge scale out of doors in these 

 brine ponds. 



Table 22 records the living contents of samples of brine taken from six salterns. 

 This table contains the observations made in the field (of temperature, cloudiness, con- 

 dition of the salterns as to color, etc.) and the results of microscopic examination in the 



