CHAPTER IT 



THE PHYSICAL BASIS OF INHERITANCE 



" Gebt mir Materie, und ich will daraus eine Welt schaffen." KANT. 



" We may regard the nucleus of the cell as the principal organ of 

 inheritance " (a prophecy proved true). HAECKEL, Generelle Morpho- 

 logie, 1866, vol. i. p. 288. 



" The cell is not only the seat of vital activity, but is also the vehicle 

 of hereditary transmission ; and the life of successive generations of 

 living beings shows no breach of continuity, but forms a continuous vital 

 stream in which, as Virchow said, rules an ' eternal law of continuity.' " 

 WILSON, 1900, p. 76. 



i. What is true in the Great Majority of Cases. 



2. Diverse Modes of Reproduction. 



3. The Hereditary Relation in Unicellular Organisms. 



4. The Hereditary Relation in the Asexual Multiplica- 

 tion of Multicellular Organisms. 



5. Nature and Origin of the Germ-cells. 



6. Maturation of the Germ-cells. 



7. Amphimixis and the Dual Nature of Inheritance 

 in Sexual Reproduction. 



8. Inheritance in Parthenogenesis. 



9. Wherein the Physical Basis precisely consists. 



i. What is true in the Great Majority of Cases 



The Inheritance is usually carried by the Germ-cells. 



What was for so long quite hidden from inquiring minds, or but 

 dimly discerned by a few, is now one of the most marvellous of 

 biological commonplaces that the individual life of the great 

 majority of plants and animals begins in the union of two minute 

 elements the sperm-cell and the egg-cell. These microscopic 

 individualities unite to form a new individuality, a potential 

 offspring, which will by-and-by develop into a creature like to, 

 and yet different from its parents. If we mean by inheritance 



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