ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



Fauna of Salt Lakes.* — B. Florentiu has studied in detail the 

 fauna of the salt lakes of Lorraine, with special reference to such 

 questions as the origin of the fauna, the nature and cmse of the vari- 

 ations known to occur in the forms inhabiting these lakes, the question 

 of acclimatisation, and so on. He believes that too much stress has 

 been laid on the chemical nature of the surrounding medium, in dis- 

 cussions on the faunas of fresh and salt water, for there is renson to 

 believe that differences in temperature, food supply, &c, are of great 

 importance in determining the nature of the different faunas. He also 

 finds, in regard to forms which inhabit equally fresh- water and saline 

 lakes, that only a small number slow notable variation as a result of 

 change of medium ; most of them manifest no marked external modifica- 

 tion. Again, a comparison of members of a species taken respectively 

 from fresh water, the sea, and saline lakes, shows that it is not the salinity 

 in itself which produces variation, but rather the diet and other factors, 

 such as temperature. Thus the marine variety of Actinophrys sol does not 

 occur in the lakes of Lorraine, but only the fresh-water one. On the 

 other hand, forms like the sticklebacks, which have had marine ancestors, 

 show in saline lakes a closer approximation to what must have been the 

 original marine form than do the typical fresh-water forms. The complex 

 nature of the problems involved is also shown by such facts as that 

 varieties from saline lakes exhibit at times progressive variation as com- 

 pared with the typical form, and sometimes retrogressive. On the whole, 

 the resemblance between the peculiar species or varieties inhabiting 

 saline lakes and those inhabiting the sea is to be regarded as a reversion 

 to ancestral type, due to the influence of the environment rather than to 

 passive transference of such forms from the sea to the lakes. The re- 

 search, therefore, emphasises anew the plasticity of the species in a 

 changing environment. 



Colour-Change.f — Mr. F. W. Gamble gives an account of the power 

 of colour-change in animals. He discusses the changes of colour in 

 chameleon, tree-frog, fishes, cuttle-fish, and Crustaceans. The common 

 striped prawn (Leander serratus) assumes a dark brown striping when 

 placed in the dark or on a blackened surface, while, if transferred to a 

 white dish, the markings first pass through a blue phase, and then 

 become pale and almost colourless. In the case of Hippclyte varians, 

 the protective coloration is well known, but there is also change uf 

 colour. In a week a green form becomes brown if transferred to brown 

 weeds ; and a rapid change from brown to green is induced by increas- 

 ing the light intensity. This prawn also shows the periodic assump- 

 tion of a peculiar nocturnal colour. Mr. Gamble also discusses the 

 chromatophores and their control. 



Physiological Effect of Common Salt.} — Prof. Jacques Loeb con- 

 continues his ohservations upon the effect of sodium ions. He finds 

 that a pure solution of sodium chloride of the same concentration as 

 sea-water acts as a strong poison to many ( f not all) marine animals, 

 the poisonous effect being due to the Na ions. This is also true for 

 pure equimolecular solutions of calcium or potassium chloride. But in 



* Ann. Sci. Nat. (Zool.), x. (1899) pp. 209-349 (3 pis. and 4 figs). 

 t Trans. Manchester Micr. Soc. 1899, pp. 92-] 0U. 

 I Amer. Journ. Physiol., iii. (1900) pp. 327-38. 



