As an illustration of Agassiz's firm adherence to his principles of classification so clearly elaborated in his famous essay on the subject, I may be excused for giving a letter written to me a few days after I had explained to him my views regarding the systematic position of the Braciopoda:

Your statements of last Saturday haunt me and I can not rest before I have seen more of your facts concerning the Anneliden affinities of the brachiopods. The most telling evidence in your favor^[1] you have never yet alluded to, at least not in my presence. But I must be cautious and wait till I see and hear more of your facts. When and where can I see you again? This is not a question of structural complication.