THEOKY OF ORGANIC ASCENSION. 217 



precisely resemble, perhaps, that of any individual whatever 

 among the lower animals. Nevertheless, it may be said to 

 represent, at each of the above-mentioned periods, the aggre- 

 gate, as it were, of the brains of each of the tribes stated." 



Although these facts were stated by Dr. Fletcher without 

 any view to the support of the development-hypothesis now 

 under consideration, it is remarkable that the series of animal 

 forms which he here traces as representing the series of suc- 

 cessive human fo3tal developments, is the very series which, in 

 the same order of succession, made their appearance on the 

 globe during the depositions of the fossiliferous rocks from the 

 earliest to the latest. 



The foregoing are the principal arguments, fortified by many 

 minor facts and considerations, from which the author of the 

 " Vestiges" concludes that the whole system of creation, with 

 all its diversified forms, inanimate and animate, from its first 

 to its last stage of unfolding, was brought forth under the 

 operation of one grand law of progressive development, by 

 which " the simplest and most primitive type gave birth to the 

 type next above it," by which " this, again, produced the next 

 higher, and so on to the very highest, the stages of advance 

 being in all cases very small namely, from one species only 

 to another, so that the phenomenon has always been of a 

 simple and modest character." He considers that after the 

 production of the first and lowest animal form, the higher 

 type was, in all cases, produced from the lower, according to 

 the ordinary process of generation, and that its superiority to 

 its parent was, in each instance, owing to a prolongation of 

 the process of utero-gestation, aided by new and favorable 

 circumstances, by which the form next superior to the parent, 

 in the pre-ordained animal scale, was attained. A similar 

 principle of transmutation was applied also to the Vegetable 



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