Sentence:  "But this is marvellous. It might be his portrait."/ "Yes, it is an interesting instance of a <WSD>throwback</WSD>, which appears to be both physical and spiritual. A study of family portraits is enough to convert a man to the doctrine of reincarnation. The fellow is a Baskerville—that is evident." 
Meaning of the word marked with <WSD> tags:  A person similar to an ancestor, or something new similar to what already existed.