382 ADAPTIVE VARIATIONS. 



Upon acclimatisation to saline solutions a consider- 

 able number of observations has been made, especially 

 in the case of Protozoa. As long ago as 1869 Czerny * 

 experimented on amoebae, and found that by the very 

 gradual addition of salt, he could acclimatise them to a 

 4 per cent, solution. With the unacclimatised organ- 

 isms, the sudden addition of .33 per cent, of salt had in 

 many cases a fatal effect, though some were able to 

 stand even a 1 per cent, solution. None could resist a 

 2 per cent, solution, however. More recently Massart t 

 has made quantitative determinations of the acclimati- 

 sation of certain ciliated infusoria to solutions of potas- 

 sium nitrate. Unacclimatised cysts of Vorticella nebu- 

 lifera first began to show plasmolysis when the strength 

 of the potassium nitrate solution in which they were 

 placed amounted to 1.2 per cent. On the other hand, 

 cysts previously kept 22 hours in a 1.8 per cent, solution 

 did not show any plasmolysis until the concentration was 

 raised to 2.5 per cent. Observations on Colpoda cucul- 

 lus gave similar results. The degree of effect produced 

 by a .8 per cent, solution in unacclimatised organisms 

 required a 2.5 per cent, solution in organisms previ- 

 ously kept 22 hours in 1.8 per cent, solution. The 

 capacity for acclimatisation varies greatly in different 

 organisms, for Bichter $ succeeded in acclimatising 

 Tetraspora to 16 per cent, sodium chloride solution, 

 whilst Spirogyra, similarly treated, was unable to resist 

 even a .5 per cent, solution. 



The acclimatisation of certain of the rnetazoa to 



*Arch. f. mik. Anat., Bd. v. p. 158, 1869. 

 t Arch, de Biol., ix. p. 515, 1899. 

 t Flora, 1. p. 4, 1892. 



