_On Alternation of Generations_, p. 80.
Haeckel’s classification of the phenomena, 80. Proposed modification,
81. Derivation of metagenesis from metamorphosis, 82. Primary
and secondary metagenesis, 84. Seasonal dimorphism related to
heterogenesis, 86. Heterogenesis and adaptation, 89. Differences
between seasonal dimorphism and other cases of heterogenesis, 89. The
case of _Leptodora Hyalina_, 93.