Vii "THE ORIGIN OF SPECIES" 235 



years, has remained unique, was discovered ; and 

 it is an animal which, in its feathers and the 

 greater part of its organisation, is a veritable 

 bird, while, in other parts, it is as distinctly 

 reptilian. 



In 1868, I had the honour of bringing under 

 your notice, in this theatre, the results of investi- 

 gations made, up to that time, into the anatomical 

 characters of certain ancient reptiles, which 

 showed the nature of the modifications in virtue 

 of which the type of the quadrupedal reptile 

 passed into that of a bipedal bird ; and abundant 

 confirmatory evidence of the justice of the con- 

 clusions which I then laid before you has since 

 come to light. 



In 1875, the discovery of the toothed birds of 

 the cretaceous formation in North America by 

 Professor Marsh completed the series of transitional 

 forms between birds and reptiles, and removed 

 Mr. Darwin's proposition that " many animal 

 forms of life have been utterly lost, through 

 which the early progenitors of birds were 

 formerly connected with the early progenitors of 

 the other vertebrate classes," from the region 

 of hypothesis to that of demonstrable fact. 



In 1859, there appeared to be a very sharp 

 and clear hiatus between vertebrated and inverte- 

 brated animals, not only in their structure, but, 

 what was more important, in their development. 

 I do not think that we even yet know the precise 



