THE BEHAVIOE OP CERTAIN MICRO-ORGANISMS IN BRINE. 65 



A result of even a slight change in density is shown by figure 9, which represents the condi- 

 tion at 11 o'clock in the forenoon of November 21. on the surface of a 1 per cent agar-agar 

 plate of brine of 1.190 specific gravity inoculated at ll h 50 m a.m., on November 17 

 from brine of 1.200 specific gravity. Even this slight difference in density is accompanied 

 or followed by cell division. 



One result of gradual loss of water, concentration of the brine, is presented in figure 10. 

 On January 10 a sterile drop of brine of 1.050 specific gravity was inoculated from a cul- 

 ture of D. viridis on a plate of 1.105 specific gravity. On January 17 there had been a 

 large increase in the number of algae in the drop and they were thriving. This culture 

 had been kept on a glass shelf in a window and it remained there, exposed therefore to 

 alternating daylight and darkness and to gradual drying (concentration). Four weeks 

 and a half later, February 1 at ll h 17 m a.m., I drew under the camera the cell shown 

 as a. By ll h 40 m a.m. this had changed as shown in b. At the same hour on the fol- 

 lowing day it looked as in c. Two days later it (d) had a clearly marked wall, and on the 

 6th at 4 p.m. it was a completed resting cell, walled and well filled with food. Salt was 

 beginning to crystallize out at the edge of the drop of brine, thus proving the increased 

 concentration. The change thus witnessed and figured seems very slow, and it may be 

 slower than a similar change would have been out of doors; but in a saltern it would have 

 taken place at the bottom, the cell having lost its cilia or drawn them in and with them 

 losing its power of locomotion, and there the change might go on quite as slowly as in a 

 culture, for the concentration of the brine would at least be no more rapid in a saltern 

 than in a hanging drop culture. In this resting, or encysted, condition the cells appear 

 to be able to withstand very great concentration of the brine and the remarkable composi- 

 tion of "mother-liquor." 



The germination of similar resting cells is seen in figure 11, in which they are repre- 

 sented as forming a considerable number of much smaller cells. This is a germination 

 which, I believe, was experimentally produced, for on a 1 per cent agar-agar plate of brine, 

 originally of 1.025 specific gravity, many cells had gone over into the encysted condition 

 in the course of nearly four months, during which the brine had so concentrated that salt 

 had begun to crystallize out in various parts of the plate. At one side of the plate I put 

 a few drops of sterile distilled water, allowing it to diffuse unaided. In the course of a 

 day or two the resting cells divided, and (as indicated in the figure) some of the daughter 

 cells escaped through the broken or digested wall of the parent cells. I did not see any 

 cilia on these daughter cells, but I attach no other significance to this than that cilia are 

 very hard to see over agar-agar. Presumably these were ciliated motile cells, which, under 

 usual conditions, would have scattered by swimming, but which were prevented by the 

 agar-agar. These may be zoospores or they may be gametes. 



I come now to the matter of gametes and of conjugation. Unfortunately I can throw 

 only less light upon it than did Teodoresco, 1 who reports having seen, in addition to a 

 considerable number of abnormal conjugations, hundreds of others. Conjugation, accord- 

 ing to this author, occupies about 10 minutes to the stage in which the two gametes have 

 become completely merged, although the zygote has four cilia. Later changes he was not 

 able to follow, for "le zygote, qui possede des mouvements tres vifs, disparait du champ du 

 microscope, et il erre, sous cette forme, pendant un temps qui je n'ai pu determiner." 

 Nor was he able to determine the circumstance or circumstances leading to conjugation. 

 I have seen a few double cells or double individuals which looked like gametes conjugating, 

 by their opposite ends, so that each end of the small mass had a pair of cilia, but I have 

 never seen complete fusion nor anything like germination of the zygotes. I have no reason 

 to doubt that these algae form zygotes, but I have not been fortunate enough to see them 

 under conditions enabling me to recognize them positively as such. 



1 Revue generate de Botanique, vol. xvm, p. 363, 1906. 



