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