Passage Summary: The author rejects an old way of naming species (based on looks) because it doesn't agree with the current popular way of naming species (based on breeding).

Conclusion: The typological theory of species classification is an invalid or unacceptable method.

Reasoning: The typological theory fails to distinguish between 'sibling species' that look identical but cannot interbreed, which contradicts the modern mainstream biological definition of species.

Analysis: This argument assumes the mainstream theory is the 'correct' one simply because it is the mainstream one. It judges the typological theory's validity based solely on its failure to align with a different set of standards. To find the flaw, look for an answer that highlights this circularity or the assumption that the mainstream definition is the only true measure of a classification system's worth.