164 ABSTRACT OF THE INFUSIONSTHIERCHEN OF EHRENBERG. 



deposits also appeared to be composed, to the extent of nearly half 

 their volume, partly of Infusoria with silicious heads, and partly of 

 Polythalamia with calcareous heads. 



To these observations M. Ehrenberg now adds the results of his 

 recent observations upon the mud of the Nile, the deposit of which has, 

 from the remotest period, attracted the attention of the curious. He 

 has purposely compared with this mud, African deposits procured from 

 Daebbe and Ambukohl, in Dongola : from Tangeur, in Nubia ; from 

 Thebes and Gyzeh, in Upper Egypt : from Boulak, near Cahira ; and 

 from Damietta, in Lower Egypt. He has also in his possession speci- 

 mens of the ancient deposits of the Nile, which M. Parthey and Lieu- 

 tenant- General Minutoli brought to Berlin. In all these specimens he 

 has found that the Sponges, the Silicious Infusoria, and, especially 

 from the neighbourhood of Damietta, the calcareous Polythalamia of 

 the arable districts on the margin of the Nile, existed in such vast abun- 

 dance, that without going the length of asserting that they absolutely 

 predominate, still it is a fact, that there is not a particle of this soil of 

 the size of half a pin's head in which, making no allowance for the che- 

 mical changes which may have taken place, there was not one, and 

 frequently many of these animals. 



We may now, therefore, safely affirm, that the deposits in harbours, 

 and even the accumulation and the extraordinary fertility of the mud of 

 the Nile, and probably of all other river deposits, proceed not solely 

 from the gradual destruction and mechanical transport of one portion 

 of solid soil to the formation of another, no more than they are solely 

 the product of the vegetation of plants ; but, on the contrary, that they 

 result from the immensely rapid agency, hitherto scarcely recognized as 

 vital, of animal organisms, which are undiscernible to the naked eye, 

 but whose quantitative and natural limits must henceforward be inquired 

 into, and which, from this time, must be considered as possessing a very 

 important influence upon these natural phenomena. 



XXXV. AN ABSTRACT OF THE " INFUSIONSTKIERCHEN" OF 



EHRENBERG. No. 5. 



By W. Hughes Wiltshire. M.D.,M.B.S., Physician to the 

 Fore Street Dispensary, &c. 



FAMILY III. VOLVOCINA. 



POLYGASTRIC animalcules having a uniform body destitute of true ap- 



