02 THE SAI.TON SEA. 



were many browns. The number decreases as the brine concentrates again. On October 

 27 the brine had a specific gravity of 1.1975, two weeks after having had its maximum 

 specific gravity. Following this, with the lag to be expected, the number of browns in- 

 creases. This decrease in specific gravity was due to rain * and was followed by condensa- 

 tion and a decrease in the numbers of D. salina. The next decided fall in concentration 

 was recorded on December 8, after two days of rain. This was followed by an increase 

 in the numbers of D. salina and a decrease corresponding with the subsequent concentra- 

 tion of the brine. On December 29 a specific gravity of 1.0175 was recorded, after three 

 days of rain. This sudden large increase in the amount of water was fatal to an enormous 

 number of all the algte, as the other two curves also show (continuous line between circles 

 for Pyramimonas, and a broken line between circles for D. viridis). The subsequent 

 fluctuations in specific gravity are followed by corresponding fluctuations in the numbers 

 of this brown Dunaliella. 



The green species of Dunaliella (D. viridis) shows a very similar record, its numbers 

 increasing and decreasing after each increase and decrease in the proportion of water in 

 the brines, except where the increase in water is very sudden and very great. Presumably 

 the effect on the individuals in the ponds is similar to that under the microscope when 

 there is a sudden addition of water. I have never been able to cause the cells to burst, 

 even by suddenly adding a large amount of distilled water to the edge of a cover-glass 

 under which was a drop of concentrated brine containing many Dunaliellas of both species : 

 but the cells become very plump, passing from pear to ball shape, and disorganization 

 soon sets in. 



The occurrence of Pyramimonas also corresponds with the proportion of water, so 

 far as our observations go, but less is known of this alga, peculiar in form and in behavior, 

 than of the others. 



For the sake of some degree of completeness, I should add that in April 1907 there 

 occurred a species of Carteria, often in great abundance. These one-celled green alga? 

 have four cilia and appear, so far as my observation goes, in water ranging in specific 

 gravity from 1.025 to 1.040. But for some reason I have not seen them since 1907, although 

 I have always looked for them. 



CULTURES. 



In table 22 such records of the behavior of the alga3 as dividing, encysted, colonies, 

 etc., appear. It will be noticed that when the record shows conditions to be fairly uniform, 

 the behavior of the organisms is also fairly uniform. In order to learn more about the 

 connection between circumstance and action, as indicated by these one-celled plants, I 

 attempted to cultivate them in liquid and on solid media. 



In some respects the manipulation of these organisms is extremely simple. One 

 need have no fear, for instance, of a culture becoming infected or contaminated from the 

 air or from contact with unsterilized instruments; for when concentrated brines are em- 

 ployed in the culture media, they present conditions fatal to the existence of all organisms 

 adjusted to fresh or nearly fresh water. On the other hand, none of the usual fixing agents 

 which I have tried fixes the organisms in culture or freshly brought in from the salterns. 

 Also it is obviously impossible to sterilize concentrated brines by steam without lowering 

 the concentration of the brines. Boiling heavy brines is disagreeable enough, but boiling 

 a heavy brine to which agar-agar has been added is still worse. 



Although I thought I should be obliged to use silicic acid jelly to solidify the con- 

 centrated brines of the Redwood salterns late in the dry season, when salt is crystallizing 

 out, I tried the gelatine and agar-agar commonly used in bacteriological laboratories. 



' Mr. J. A. Squire, U. S. volunteer weather observer, kindly shares with me his record that 0.36 inch of rain 

 fell in Palo Alto on October 26. There was certainly no less at Redwood and there may have been more. On Decem- 

 ber 4 and 6 a total of 0.89 inch of rfun fell, and on December 27, 28, 29, a totd of 0.64, with continuous cloudiness. 



