the world > life > biology > taxonomy > taxon > [noun] > genus or sub-genus > form-genus or form-species
form-genus1873
form-species1886
1886 Encycl. Brit. XXI. 399/2 Billroth came forward in 1874 with the startling view that the various ‘form-species’ and ‘form-genera’ are only different states of one and the same organism.