1901) MICROSCOPICAL JOURNAL. 241 
Contractile vacuoles can be explained by an augmenta- 
tion of tension promoted by some endosmotic currents. 
The former may be imitated by alternatively stretching 
and relaxing a plate of gluten. 
Life ought not to be likened to a continuous chemical 
reaction, the mechanism of which remains involved in 
darkness and unexplained. Life is now to be defined as 
the result of the physico-chemical action of protoplasmic 
currents, the cause of such currents being diffusion, heat, 
and some other secondary factors. Death consists in an 
absolute suspension of the internal currents in general; 
latent life is characterised by the establishment of the 
said currents under the influence of oxygen, heat, and 
water, in a germ or organism having the structure and 
chemical elements necessary, and supplied with every 
nutriment required. Oscillating life is nothing more 
than an alternate contribution and reassertion of the 
constructive internal currents (sleep), depending upon 
the variations of the external temperature, Every phy- 
sico-chemical or mechanical action capable of affecting 
the rapidity, direction, and other characters of internal 
currents must have more or less influence on the phenom- 
ena hitherto considered as vital. 
There is a new series of proofs; the experiments of _ 
the writer on the movements and evolution of alkaline 
oleates in the Pfeffer’s solution. (See “Memorias de la 
Sociedad Alzate,’’ 1900). 
Colouring of Water by Micro-Organisms, 
BY JAMES BURTON. 
It is well known, not alone to microscopists, that large 
or small bodies of water are sometimes coloured by the 
presence of various organisms, either animals or plants, 
often of microscopic size. Every roadside pond is liable 
to become of a thick soupy appearance and green colour 
