They may become extinct, or they may endure as varieties for very long periods, as has been shown to be the case by Mr. Wollaston with the varieties of certain fossil land-shells in Madeira, and with plants by Gaston de Saporta.
Iraungi ere egin daitezke edo aldi oso luzeetan zehar aldaki izaten segi, Wollaston jaunak Madeirako lehor-molusku fosilen zenbait aldakiri, eta Gaston de Saportak zenbait landareri gertatzen zaiola frogatu duten moduan.