Full Idea
Kripke stresses that membership of a single animal species requires identity or similarity of internal structure. In my view, what matters is genetic affinity - a common descent. Internal structure is merely a clue.
Gist of Idea
Kripke says internal structure fixes species; I say it is genetic affinity and a common descent
Source
report of Saul A. Kripke (Naming and Necessity lectures [1970]) by Michael Dummett - Could There Be Unicorns? 2
Book Reference
Dummett,Michael: 'The Seas of Language' [OUP 1993], p.332
A Reaction
The crucial test question would be whether we can make a tiger artificially (even constructing the DNA). I would say that if you make a tiger, that's a tiger, so Kripke is right and Dummett is wrong. The species is what it is, not where it came from.