INFI'SORIAL ANIMALCULES. 63 



attained at the South Pole, in the enth-e cireumferenee of the globe, 

 are these organisms found. 



Their distribution in space is co-extensive with that in time ; for, 

 as in the present condition of oiu- planet, no portion of its surface 

 seems destitute of Infusorial life, so, it Avould appear, from the pi'ose- 

 cution of microscopic ix-scarch in connexion with geological facts, 

 that, under this simplest, this primary- form, organic life made ita 

 fii'st appearance on the globe. Thus, siliceous microscopic beings are 

 discoverable in the oldest rocks above the igneous, and, in many 

 instances, such beings woxild seem to have played a most important 

 part in the building up of strata. Much of the silica of flint 

 originates from the siliceous cases of extinct Bacilhria, and even 

 porphyritic rock, raised by volcanic or ig-neoua agency, is not devoid 

 of examples of such beings. 



Thus, through the many epochs of this world's history, during 

 which its surface has undergone the mightiest changes, Infusorial 

 life has been sustained ; and so surprisingly so, that forms which now 

 exist, had their specific or their generic types at the very dawn of 

 organization. This implies the extraordinai-y capability of the 

 Infusoria to preserve life, as also their no less wondei'fiil power of 

 multiplication. Yet, notwithstanding the conservative and repro- 

 ductive power of microscopic life, and its consequent capacity for 

 almost unlimited diffusion, some definite law is manifest in many 

 cases of geographical distribution. 



The untiring industiy of Professor Ehrenberg, in examining recent 

 and fossil specimens, sent to him from almost every known region of 

 the globe, has disclosed the fact, that although some species are 

 cosmopolitan, not a few may be taken as characteristic of certain 

 geographical areas. To give an example, we may quote from a 

 recent paper, read by that great microscopist, before the Berlin 

 Academy, on a very extensive layer of siHceous Polygastrica in 

 Oregon : — "The chain of rocky mountains traversing the continent 

 of North America, forms, -with reference to the distribution of 

 Infusoria, a stronger barrier between California and Oregon, and the 

 rest of the continent, than does the Pacific Ocean, with China, 

 between the Western Plains of North America, and the Region of 

 Siberia. Thus, the United States, with Mexico, never present any of 



