Full Idea
The concept of natural kinds was reintroduced by Quine, who may now regret the way it has become a stand-in for the dubious but covertly popular concept of essences.
Gist of Idea
Quine probably regrets natural kinds now being treated as essences
Source
report of Willard Quine (Natural Kinds [1969]) by Daniel C. Dennett - Consciousness Explained 12.2 n2
Book Reference
Dennett,Daniel C.: 'Consciousness Explained' [Penguin 1993], p.381
A Reaction
He is right that Quine would regret it, and he is right that we can't assume that there are necessary essences just because there seem to be stable natural kinds, but personally I am an essentialist, so I'm not that bothered.