Chapter V: Heredity and the Origin of Variations

Heredity in the protozoa 123
Regeneration of lost parts 124
Sexual reproduction and heredity 129
The problem of hen and egg 130
Reproductive continuity 131
Pangenesis 131
Modified pangenesis 134
Continuity of germ-plasm 138
Cellular continuity with differentiation 142
The inheritance or non-inheritance of acquired characters 146
Origin of variations on the latter view 149
Hypothesis of organic combination 150
The extrusion of the second polar cell 153
The protozoan origin of variations 156
How can the body influence the germ? 159
Is there sufficient evidence that it does? 162
Summary and conclusion 175

CHAPTER VI.
ORGANIC EVOLUTION.

The diversity of animal life 177
The evolution theory 181
Natural selection: not to be used as a magic formula 183
Panmixia and disuse 189
Sexual selection or preferential mating 197
Use and disuse 209
The nature of variations 216
The inheritance of variations 223
The origin of variations 231
Summary and conclusion 241