Hybrids and mongrels compared, [272].
Hybridism, [245].
Hydra, structure of, [190].
I.
Ibla, [148].
Icebergs transporting seeds, [363].
Increase, rate of, [63].
Individuals, numbers favourable to selection, [102].
——, many, whether simultaneously created, [355].
Inheritance, laws of, [12].