DISTRIBUTION. 407 



hypothesis that the successively-higher types fossilized in our 

 successively-later deposits, indicate nothing more than suc- 

 cessive migrations from pre-existing continents to continents 

 that were step by. step emerging from the ocean — migrations 

 which necessarily began with the inferior orders of organ- 

 isms, and included the successively-superior orders as the 

 new lands became more accessible to them and better fitted 

 for them.* 



While the evidence usually supposed to prove progression is 

 thus untrustworthy, there is trustworthy evidence that there 

 has been, in many cases, little or no progression. Though the 

 orders which have existed from palaeozoic and mesozoic times 

 down to the present day, are almost universally changed, yet 

 a comparison of ancient and modern members of these orders 

 shows that the total amount of change is not relatively great, 

 and that it is not manifestly towards a higher organization. 

 Though nearly all the living forms which have prototypes in 

 early formations differ from these prototypes specially, and 

 in most cases generically, yet ordinal peculiarities are, in nu- 

 merous cases, maintained from the earliest times geologically 

 recorded, down to our own time; and we have no visible evi- 

 dence of superiority in the existing genera of these orders. In 



* For explanations, see " Illogical Geology." Essays^ Vol. I. How much 

 we may be misled by assuming that because the remains of creatures of high 

 types have not been found in early strata, such creatures did not exist when 

 those strata were formed, has recently (1897) been shown by the discovery 

 of a fossil Sea-cow in the lower Miocene of Hesse-Darmstadt. The skeleton 

 of this creature proves that it differed from such Sirenian mammals as the 

 existing Manatee only in very small particulars: further dwindling of dis- 

 used parts being an evident cause. If, now, we consider that since the 

 beginning of Miocene days this aberrant type of mammal has not much 

 increased its divergence from the ordinary mammalian type ; if we then 

 consider how long it must have taken for this large aquatic mammal (some 

 eight or ten feet long) to be derived by modification from a land-mammal ; 

 and if then we contemplate the probable length of the period required for the 

 evolution of that land-mammal out of a pre-mammalian type ; we seem car- 

 ried back in thought to a time preceding any of our geologic records. We 

 arc shown that the process of organic evolution has most likely been far 

 slower than is commonly supposed. 

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