Vertebrate Embryos and Medusae 45 



of mind which was so characteristic of him in his deal- 

 ings with philosophy and tradition. He never allowed 

 any weight of authorit}'- or any apparent disturbance of 

 existing ideas to alter the conclusions to which his 

 reason led him. This intellectual courage made him 

 fitted to be the leader in the battle for evolution and 

 against traditional thought, and we shall find again 

 and again in consideration of his work that it was the 

 keynote of his life. 



