ij HISTORICAL 11 



and Darwin. The subsequent literature is full of 

 devices for the mechanical dispersal of animals, as 

 marine currents, floating logs and icebergs, storms 

 and waterspouts. 



Wallace's method of arriving at the degree of 

 relationship of the faunas of the various regions 

 is eminently statistical. Long lists of genera deter- 

 mine by their numbers the affinity and hence the 

 source of colonisation. This statistical method has 

 found many followers, who, relying more upon quantity 

 than quality, have obscured the problem. 



An extensive literature has since grown up, almost 

 bewildering in its range, diversity of aims, and style 

 of procedure. So prominent, as to almost constitute 

 a characteristic period, has become the search by 

 specialists for either the justification or the amend- 

 ing of the Sclater- Wallace regions. As class after 

 class of animals was brought up to reveal the secret 

 of the true regions, some authors saw in their 

 different results nothing but the faultiness of the 

 regions established by their predecessors ; others 

 looked upon eventual agreements as their final cor- 

 roboration, especially when such diverse groups as, 

 e.g. mammals and scorpions, could, with some in- 

 genuity, be made to harmonise. But the undeniable 

 result of all these efforts was the growing knowledge 

 that almost every class, nay many an order or even 

 family, seemed to follow principles of its own. The 



