88 EXPLANATIONS. 



pods and cephalopods, though not of such high 

 forms as afterwards appeared. I might here 

 repeat what was remarked in the later editions 

 of the Vestiges, " Even though the cephalopoda 

 could be shown as pervading all the lowest fos- 

 siliferous strata, what more would the fact denote 

 than that, in the first seas capable of containing 

 any kind of animal life, the creative energy ad- 

 vanced it, in the space of one formation, (no one 

 can tell how long a time this might be,) to the 

 highest forms possible in that element, excepting 

 such as were of vertebrate structure." I might 

 add, that this was no great advance in comparison 

 with the whole line of the animal kingdom, if we 

 may take, as a criterion on this point, the analo- 

 gous progress of an embryo of the highest animals, 

 as the portion of that progi-ess representing the 

 organization of the invertebrated animals is only 

 the first month. I might here also revert to the 

 book for some views with respect to the space 

 required for such a development. According to 

 the plan of animated nature, to which I have 

 made approaches in the later editions, we have 

 not to account for the development of one long 

 line, but of many comparatively short ones. 



