For any form existing in lesser numbers would, as already remarked, run a greater chance of being exterminated than one existing in large numbers; and in this particular case the intermediate form would be eminently liable to the inroads of closely allied forms existing on both sides of it.
Egon ere, banakotan urri existitzen den forma oro, ugari dena baino sakailatua izateko arrisku hadiagoan dago; eta kasu partikular honetan, bitarteko forma, bere alde bietan bizi diren forma oso hurbilen inbasioen arrisku handitan legoke.