68 ON INFUSORIA IN THE MUD OF RIVERS, ETC. 



Finally, that this substance does not belong to the enamel of the 

 teeth, will be readily perceived by every one who has inspected the 

 enamel itself.* 



Explanation of the Figures, Plate 2, Division 1. 



Figs. 1, 3, & 4, Show the thread-like bodies as described under No. 1. 



Fig. 2. Second form of the thread-like bodies, separated, and with a portion of 



epithelium. 

 Fig. 5. Third form of the thread-like bodies, surrounded by the granular mass, in 



which the fibres are sometimes very distinct. 

 Fig. 6. Single fibres of the thread-like bodies, some entire, and others probably 



broken. 

 Figs. 2 & 6, Are drawn under higher magnifying powers than the other figures. 



XII. OBSERVATIONS ON THE PROBABLE SOURCE AND EXTENT OF 



INFUSORIA IN THE MUD OF RIVERS, ETC.f 



By T. F. Bergin, Esq., of Dublin. 



EHRENBERG, who has already reaped such abundant laurels by the appli- 

 cation of the Microscope to the Arcana of Nature, has, during the last 

 year made another very important communication to the Berlin Academy, 

 a translation of which by Mr. Weaver, has recently appeared in 

 Jameson's Philosophical Journal, and of which I observe an abstract in 

 the Microscopic Journal, Vol. I. p. 162. 



I refer to his Observations on the important part which Microscopic 

 Organisms play in Choking up certain Harbours. 



Having made the truly wonderful discovery, now so familiar to every 

 microscopist, that extensive apparent mineral beds, and, in some in- 

 stances, almost mountain ranges, are composed almost exclusively of the 

 silicious or calcareous shells of animalcules, so minute, as not merely to 

 be invisible to the naked eye, but even to require high magnifying powers 

 to establish their existence, he was naturally led to inquire whether 

 similar causes were still in operation, and has arrived at the conclusion 

 that a very large proportion of the mud banks deposited by certain rivers 

 flowing into harbours, consists of these organisms in the living state. 

 In fact, a moderate estimate, b ised upon microscopic examination of the 



* From Miiller's Archiv. 1840. 



f Read before the Microscopical Society of Dublin, January 1842, and communi- 

 cated by the Author. 



