ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 773 



when otherwise they would remain invisible. There is nothing new 

 in this method of examination ; it is an application of the process 

 employed by Prof. Tyndall to prove the optical purity of air, but it 

 does not appear to have been put into practice up to the present. It 

 has led the author to what he considers a conclusion of the very 

 highest interest, viz. the constant presence of certain corpuscles in all 

 the waters of Caux and which he is now certain will be found in the 

 natural waters of all countries. 



These corpuscles are hyaline and endowed with a refractive 

 power about equal to that of water. Amongst them are some which 

 present vacuoles filled with water or gas. Others appear under the 

 form of disks, similar to the discoid diatoms. They all have a 

 density greater than that of sea water (1-026) which contains myriads 

 of them, at least at Fecamp. They resist the attacks of dilute 

 mineral acids and also of dilute caustic alkalies. They were found 

 in all the waters which the author has been ajale to examine hitherto ; 

 sea water, spring water, well water, running water, rain water, and 

 even in distilled water which has been for some time exposed to 

 contact with the air, which leads to the belief that they are also dis- 

 persed in the atmosphere. 



Although about 2 mm. in diameter they are so flexible and plastic 

 that they pass through the finest filters ; for a great number of those 

 which are contained in drinking water pass through the kidneys and 

 are found again in the urine. 



The germs of Euglence exist among these corpuscles, and this 

 circumstance explains the profusion with which green substances, 

 especially that bearing the name of Priestley, are developed in all the 

 places exposed to solar light, direct or diffused, and to damp. 



Amongst these little organisms there are some which appear to the 

 author to play an eminently active part in the purification of waters 

 charged with organic matters in a state of putrefaction, or capable of 

 entering into putrefaction, when these waters, either running or 

 stagnant, are exposed to contact with the air. We know that the sub- 

 stances in question are then oxidized and are transformed into 

 carbonic acid and ammonia, or into nitric acid. Hitherto it has been 

 admitted that the intervention of the combustive element is manifested 

 by a direct action. The author is now led to believe that this 

 intervention is only the consequence of a phenomenon of nutrition, 

 undergone by some of the corpuscles in question, perhaps even by all. 

 With respect to this he has begun a series of experiments and observa- 

 tions the results of which he intends later on to submit to the 

 Academy. The present communication is chiefly made to establish 

 priority, " but, in any case, the profusion with which these non- 

 microscopic little beings are diffused ought, it seems to me, to be 

 considered as a certain sign of the importance of the role which they 

 are destined to play in nature." 



Ser. 2.— Vol. IIL 3 F 



