CONTENTS. 



VITALITY. 



Introduction 5 



Ontogenetic Perplexities , 6 



Molecular Theories Examined 10 



(a) Polarigenisis — Herbert Spencer 10 



(b) Pangenesis — Darwin 12 



(c) Perigenesis — Ildeckel 14 



(d) Mcchanico-Pliysiological Theory — Naegeli 16 



(e) The Continuity of Germ-Plasm — Weismann 20 



Summary 25 



The LivrNC, Substance and Its Properties. 



Introduction 30 



Vital Motility : 31 



Assimilation : 40 



Depuration 45 



Growth and Reproduction 46 



General Remarks 50 



ORGANIZATION. 



Introduction 53 



The Unity of the Oi'ganic Individual ..♦ 54 



Organic Differentiation 58 



Germ-Plasm and Its Organization 62 



Segmentation 68 



Formative Stimulation - 71 



Fertilization 72 



The Problem of the Living Form 79 



