INFERENCES. “My own hypothesis of the transfer of larval forms depends on genetic mechanisms that are imperfectly understood but that can be inferred.” Just as Darwin’s work operated in the absence of modern genetics.
https://books.google.es/books?hl=en&lr=&id=4Bv_CAAAQBAJ&oi=fnd&pg=PR3&dq=evolution+of+larval+stage&ots=Ajv40BxpV8&sig=UoAuSNQhyUJxvYurqij18mPF3GM