Comments on AW’s work [Einfluss der Isolierung (1872)].
Discusses formation of local races.
Conchologist should investigate whether species of same genus vary during successive geological periods.
Comments on Franz Hilgendorf ["Über Planorbis multiformis", Monatsber. K. Preuss. Akad. Wiss. Berlin (1866): 474–504].
Believes sexual selection will be judged a powerful agency.