Palaeontology. 171 



ments of biology, so here we have to note that mutual 

 influence of the ruling doctrine and the concrete investi- 

 gations which has been so characteristic of progress in 

 the Darwinian era. 



On the one hand, the doctrine of evolution has given 

 the palaeontologists fresh inspiration and a new ambi- 

 tion. As Von Zittel puts it, "Palaeontology has long 

 ceased to place itself exclusively at the service of 

 geology as the study of characteristic fossils. . . . To 

 determine the genetic relationships, the ancestry, the 

 modification, and the further development, in short, the 

 race-history or phylogeny, of the organisms under con- 

 sideration is now regarded as the essential, by many 

 indeed as the chief aim of palaeontology." 



No one has dealt with the so-called palaeontological 

 evidences of evolution more forcibly, and at the same 

 time more rigorously, than Huxley did, and it is very 

 instructive historically to read his addresses to the 

 Geological Society of London in 1862 and in 1870. In 

 the former address he asked, "What then does an im- 

 partial survey of the positively ascertained truths of 

 palaeontology testify in relation to the common doctrines 

 of progressive modification, which suppose that modifi- 

 cation to have taken place by a necessary progress 

 from more or less embryonic forms within the limits of 

 the period represented by the fossiliferous rocks?" 

 And his answer was, "It negatives those doctrines; 

 for it either shows us no evidence of any such modifi- 

 cation, or demonstrates it to have been very slight ; and 

 as to the nature of that modification, it yields no evi- 

 dence whatsoever that the earlier members of any long- 

 continued group were more generalized in structure 

 than the later ones". 



In the second address, eight years later, he gladly 

 found reason to soften his "somewhat Brutus -like 

 severity", while still insisting that "it is no easy matter 

 to find clear and unmistakable evidence of filiation among 

 fossil animals". " It is easy", he said, "to accumulate 

 probabilities hard to make out some particular case in 

 such a way that it will stand rigorous criticism." As 

 to the Invertebrates and lower Vertebrates, the evidence 



