134 GEOLOGICAL DISTRIBUTION. 



self in all the geological formations that are known to us, from the 

 Cambrian period to the present day, and there can be no doubt 

 that, were a fossiliferous formation discovered of older date than 

 the Cambrian, or immediately underlymg it, we should find pre- 

 cisely the same juxtaposition, although to a more limited extent, of 

 organisms of higher and lower development. Only then when we 

 could fathom the first-born deposit, or trench upon the period 

 when life first came into existence, would we, in all probability, be 

 circumscribed in our survey to animals exhibiting a nearly uniform 

 low grade of organisation. Such a point has probably not yet 

 been reached, or, if reached, its existence can only be indicated 

 with doubt, since the oldest rock deposits (the Laurentian) into 

 whose composition an organic element unquestionably largely en- 

 tered have lost all or nearly all traces of their primary fossiliferous 

 character. With this wholesale obliteration have, consequently, 

 disappeared the traces of the earliest and most primitive types of 

 life-forms. 



If Eozoon and Archseospherina, from the Laurentian limestones, 

 be considered actually to represent organic forms, as is maintained 

 by many prominent geologists and naturalists, then, indeed, are we 

 presented with a large series of deposits in which apparently all 

 the organic elements belong to one uniformly low type — the type 

 of the Foraminifera — not yet the lowest, but very nearly it. But 

 even granting the animal nature of the two structures here indi- 

 cated, it would yet be very unsafe to affirm that they represent 

 the only forms of life that tenanted the earliest seas; multitudes 

 of other forms may have flourished and perished, and left no 

 traces behind them, or had their traces completely obliterated at 

 some remote subsequent period. We should then be no wiser for 

 their existence. The succeeding Cambrian period ushers in with 

 it such a host of multiform beings — beings of comparatively high 

 organisation — that it becomes almost impossible to conceive that 

 their ancestry should date back only to a period so little removed 

 from the Cambrian as the Laurentian, unless, indeed, the hiatus 

 separating the Laurentian from the Cambrian is very much greater 

 than is indicated by its stratigraphical position. But if the an- 

 cestral forms of the Cambrian stock already existed in the Laurentian 

 seas, what has become of their remains ? Why is it that in these 

 oldest so-called fossiliferous rocks we meet with only Eozoon and 



