154 The Scottish Naturalist. 



palaeontological history. Even fishes and reptiles, if we count- 

 (not weigh) them, how profuse soever in generic types in pre- 

 vious formations, abound still more in these — the flourishing 

 period of their fellow vertebrates. So that, in regard to this 

 third class of circumstances influencing favourably the working 

 of natural selection in evolving diversity of forms, the scale 

 again preponderates in favour of the recent formations. One 

 more set of conditions adding intensity to the genus-differenti- 

 ating process falls on a time when the law of polarity asserts a 

 maximum production of genera. And thus, on the whole, it 

 cannot be said that there are awanting facts either to establish 

 the law or to unfold the cause, that the commencement of 

 organic development has been inaugurated, and the goal of its 

 perfection signalised, by a profuse origination of generically- 

 distinct organisms. 



It may be said that the above view and treatment of this 

 theory makes it a very different thing from what it was in the 

 hands of its author. It concerns genera, but with Forbes a 

 genus was not anything for the origination of which Darwinism 

 could render a reason. Also, while the theory concerns a 

 numerical variation in the genera produced at different times, 

 its author contemplated no physical agency intermediate be- 

 tween the creator and his generic creations. But, as has 

 already been indicated, taking Polarity in itself as simply a 

 generalisation of the facts concerned, and irrespective of its dis- 

 coverer's concomitant doctrines, it is perfectly indifferent whether 

 genera were created immediately or by evolution, whether the 

 external conditions were suited with the proper forms of life by 

 immediate creation, or they suited themselves with their appro- 

 priate forms by natural selection and the survival of the fittest. 

 Other generalisations of the same theorist, such as that of 

 generic centres (see Jukes' Manual of Geology, p. 492, 1873 ) 

 admit of being easily wrought into the texture of the Darwinian 

 hypothesis — a fact that may do something in the way of 

 verifying both it and them ; and Polarity, the widest, and if you 

 will, the wildest, of them all, suffers change only in the relations 

 it held to his other scientific opinions, not in its essence, when 

 it is similarly treated. Mr. Wallace says this theory died a 

 natural death long ago — the natural death of all false theories, 

 a fjte from which ; he adds, the great name of its author could not 



