Specialization, [236], [239]

Struggle for existence, [11], [158], [277]; mitigation of, [217]

Surface and mass, [35], [50]

Tissues, [42]

Turbellaria, [46], [102]

Vertebrates, [73], [81], [107]; primitive, [77]

Volvox, [40]

Weismann, [290]

Will, [136]

Worms, [56]; schematic, [52]