Sentence:  A few naturalists, <WSD>endowed</WSD> with much flexibility of mind, and who have already begun to doubt on the immutability of species, may be influenced by this volume; but I look with confidence to the future, to young and rising naturalists, who will be able to view both sides of the question with impartiality. 
Meaning of the word marked with <WSD> tags:  "Usually in the (passive)": to naturally furnish (with something).