THE GEOLOGICAL METHOD. 411 



globe is the entire series of the strata-system perfect, with 

 layer on layer in due succession ; in no place is the series even 

 approximately complete. In fact, the order of the different 

 strata of the earth and of the corresponding periods of the 

 earth's history, as commonly conceived by geologists, is only 

 hypothetical, and does not actually exist ; it is the result of 

 the comparison of a number of separate observations of the 

 sequence of strata at various points on the earth's surface. 



We shall treat the Phylogeny of Man in a similar way. 

 We will endeavour to form the various phylogenetic frag- 

 ments, occurring in very different groups of the animal 

 kingdom, into an approximately correct representation of 

 the ancestral line of Man. We shall find, that it is really 

 possible, by rightly grouping and comparing the germ-history 

 of very diverse animals, to obtain an approximately perfect 

 picture of the palseontological development of the ancestors 

 of Man and of Mammals ; a picture, such as could never be 

 formed from the Ontogeny of the Mammals. In consequence 

 of the kenogenetic processes to which we have alluded, in 

 consequence of vitiated and of abridged heredity, whole 

 series of the lower stages of evolution, especially in the most 

 ancient periods, have fallen out from the germ-history of 

 Man and of other Mammals, or have been vitiated by modifi- 

 cation. But in the lower Vertebrates and in their Inverte- 

 brate ancestors we meet with these very low form-stages 

 in all their original purity. Especially in the lowest of all 

 Vertebrates, the Amphioxus, the most ancient ancestral forms 

 have been perfectly retained in the evolution of the germ. 

 So, too, we find strong evidence in the Fishes, which stand 

 midway between the lower and higher Vertebrates, and 

 which explain several other phylogenetic periods. Lastly 

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