CONTENTS. XI 



Pages 

 Sexual selection operating as between different spermato- 



zoids. — Movements of the female element. — Vegetable 

 fecundation. — Progressive differentiation of the two sex- 

 ual elements. — Sexual reproduction of the Ectocarpus sili- 

 culosus, after Berthold. — Investigations of Pfeffer upon 

 the spermatozoids of cryptogams.— Action 6f certain 

 chemical excitants upon these elements. — Specific charac- 

 ter of the excitant. — The threshold of excitation. — Appli- 

 tion of Weber's law 75-91 



THE PHYSIOLOGICAL FUNCTION OF THE 

 NUCLEUS. 



Functions attributed to the protoplasm and to the envelop- 

 ing membrane. — The nucleus, its histological importance 

 proved by the phenomena of caryokinesis. — Balbiani and 

 Gruber have, at times, observed Infusoria and Actinophrys 

 deprived of nuclear substance. — Nussbaum's and Gruber's 

 experiments of vivisection upon the Slentor -cceruleus. — 

 Fragments provided with nucleus reconstruct themselves. 

 — Experiments of Balbiani — Facts observed by Gruber, 

 in general, confirmed. ^Error of Gruber respecting frag- 

 ments without nucleus. — These fragments do not con- 

 tinue to live, their plasma undergoes disorganization. 

 — Experiments of division. — Experiments made upon 

 Infusoria while in conjugation. — The presence of the 

 old nucleus id a severed fragment only brings about 

 an incomplete regeneration. — The nucleus presides over 

 all physiological functions, the totality of which con- 

 s|itutes life. — The regenerative and reproductive property 

 of the plasma is lost before the psychical functions are. — 

 Agreement of all these facts with the phenomena ob- 

 served as taking place during the spontaneous division of 

 Micro-organisms 92-105 



CONCLUSION. 



Statement of M. Richet's position respecting cellular psy- 

 chology i 105 



