184 Mr Morren on the Gases of Stagnant Waters, &c. 
At the moment when the oxygenation of the water is at its height, 
great numbers of infusory animalcules, furnished with ciliary and rotatory 
apparatus, make their appearance ; they descend below the surface, when 
the enchelides on which they prey likewise descend along with them. 
In recapitulating the facts deduced from these experiments, the author 
thinks he has proved that, with the assistance of light, the green animal- 
cules which live in stagnant waters decompose the carbonic acid con- 
tained in it, and absorb its carbon, and that the oxygenated gas disen- 
gaged dissolves in the water in the state of a nascent gas. 
The oxygenation of the water diminishes in proportion as we descend 
below the surface ; thus, at 3 feet, the air of the water contained 43 parts 
in 100 of oxygen, while there were only 34 parts in 100 at the depth of 
18 feet. 
The maximum of oxygenation runs from 56 to 61 in 100, and takes 
place about four or five o’clock in the evening. 
It was important to ascertain whether the green colour was indispen- 
sable to the existence of the property of decomposing the carbonic acid 
in the microscopic infusory animalcules living in stagnant water. After 
many fruitless researches, Mr Morren at length succeeded in procuring 
the means of reproducing a great number of an animalcule of a fine 
purple colour, which he at first took for a Protococeus nivalis, but which 
he afterwards found to be nearly allied to Tvrachelomonas volvocina of 
Ehrenberg. He filled numerous bell glasses, containing from eight to 
ten litres with filtered rain water. He then poured into each of them 
half a litre of water well replenished with trachelomonas, and at the end 
of a month, all his vessels were shining with a magnificent reddish-purple 
colour. 
He then had it in his power to repeat with these animalcules all the 
experiments he had made on the green ones, and he obtained results ab- 
solutely identical. Only the proportion of oxygen never exceeded at the 
maximum 47 per cent., instead of 61 obtained in the fish pond ; but it 
is easy to perceive that the artificial conditions of life in which tlic 
' trachelomonas were placed may explain these differences. It is evident, 
therefore, that the green colour of the animalcules is not an indispen- 
sable element in the decomposition they cause of the carbonic acid con- 
tained in the water; that the phenomenon is reproduced with those of 
ared colour, and that it is probably also an attribute of animalcules of 
every colour and condition of existence. This constitutes another bond 
of connection between the two great kingdoms of the organic creation, 
and a new and powerful agent in the purification of the atmosphere.* 
* From Bibliothéque Universelle de Geneve, No. 1xx., Oct. 1841, p. 386. 
