CONTENTS. XV 



CHAPTER H. 

 OF THE INFLUENCE OF PHYSICAL AGENTS ON THE ORGANIC SERIES. 



Of the Geography of Plants: their horizontal and vertical Localization. Influence of Heat on or- 

 ganic Distribution : isotheral and isochimenal Conditions. Effects of Variations in the Dens- 

 ity of the Air, Moisture, Soil, Sunlight, Length of Day. Definite Quantity of Heat required 

 by Plants. 



Secular Perturbations in the Species of Plants. Long Periods of Time required. Secular geo- 

 logical Changes. 



Inverse Problem of the Investigation of the Earth's History from her fossil Flora. Two great 

 terrestrial Epochs : Change in the Constitution of the Air, and Localization of Organisms 

 through Decline of the Earth's Interior Heat. 



Difference between abrupt and gradual Impressions. Invariable Causes may produce abrupt 

 Crises. 



Extension of the above Principles to the Case of Animals. Case of the Inca Indians. 



General Argument supported by the Extinction of Forms. Development is under the Influence of 

 Law. Rudimentary Organs and Excesses of Development. The Idea of Development by 

 Law consistent with natural Facts Page 472 



CHAPTER HI. 



OF THE ORGANIC CELL : ITS DEVELOPMENT. REPRODUCTION, AND DIFFERENTIATION 

 OF STRUCTURE AND FUNCTION. 



Simple and Nucleated Cells. The Simple Cell: its Parts and Functions. The Nucleated Cell: 

 its Parts and Functions. Activity of the Nucleus. Other Forms of Cells. Cells arise by 

 Self-origination and Reproduction. Reproduction by Subdivision and Endogenously. 



The Animal Cell. Forms of Cellular Tissue. Forms of Vascular Tissue. Spiral Vessels, 

 Ducts, etc. 



Differentiation of Cells. Acquisition of new Functions. Differentiation of the Animal Cell. 

 Depends on Physical Causes. Influence of Heat and Air. Epoch of Differentiation.... 492 



CHAPTER IV. 

 OF REPRODUCTION AND DEVELOPMENT. 



Relation of Organic Beings : they come from a similar Cell and develop to different Points. 

 Their Division by Classification is fictitious. Development and Differentiation. Homogenesis 

 and Heterogenesis. They depend on physical Conditions. The reproductive State closes De- 

 velopment. 



Development is from the General to the Special. Law of Von Bar. Invariable Sequence in 

 Differentiation. 



OF REPRODUCTION: 1st. By Generation. Conjugation and Filaments. The Sperm-cell: its 

 Production. Spermatozoa. The Germ-cell: its Production. 



Ovum in the Ovary. Its Structure. Corpus Luteum. 



Ovum in the Oviduct. Mulberry Mass. Germinal Membrane. The Chorion. 



Ovum in the Uterus. Membrana Decidua. Placenta. Development of the Embryo. Types 

 of Nutrition. Of Conception. Of Gestation. Of Parturition. Influence of both Parents. 



2d. By Gemmation. Budding of Plants and Animals. Of Grafting. Limit of Gemmation. 

 Influence of Temperature on Gemmation. 



Alternations of Generation. Its Explanation 505 



CHAPTER V. 



THE GROWTH OF MAN. 



Infancy. Weight and Size of the Infant. Weight and Size at subsequent Periods. Develop- 

 ment of the Intellect. Maturity of Man. Tendency to Crime. Maxima of Physical and Men- 

 tal Strength. 



