22 Teachings of Thomas Huxley 



have no hesitation in pointing out at once any 

 change of opinion. 



THE METHOD OF DISTRIBUTION. 



The distribution of animals and plants was 

 a difficult thing to explain in connection with 

 evolution, and although Mr. Darwin attempted 

 it, his ideas on the subject were at the time 

 scarcely acceptable. Huxley held that in a 

 given epoch and a given area the Fauna and 

 Flora can consist only of life that descended 

 from the immediately preceding epoch. It is 

 necessary to allow, however, for transformation 

 of geographical features, in which case living 

 forms from some other area might migrate into 

 the given area and hence cause confusion as to 

 similarity of biological form in different geo- 

 logical structures. There are two main hy- 

 potheses to be considered, he thinks, in ac- 

 counting for distribution of life: 1. That dis- 

 tinct provinces of distribution have existed 

 since the earliest date at which the life of 

 any period is recorded, and possibly much 

 earlier. 2. That progressive modification of 

 terrestrial forms is more rapid in areas of ele- 

 vation than in areas of depression ; and that 

 in the Permian epoch there was an upheaval 

 of North America, Europe, Asia, and Africa, 

 hence reptiles, birds, and mammals rapidly 

 spread into the new area from outlying prov- 



