PART I. KARYOKINESIS. 



CONTENTS. 



Introduction .............. 5 



Methods 6 



I. Maturation. 



A. Predivision Stages ............. 7 



1. The Ovarian Egg 7 



2. Egg Laying ............. 8 



B. Maturation Divisions 8 



1. Nuclei ; . . 8 



a. Chromatin ............ 8 



b. Nuclear Sap . . . . ... . . . . . .9 



c. Nucleolus 10 



d. Chromosomes ' 10 



2. Centrosomes and Central Spindles 14 



3. Polar Rays, Spindle Fibres and Spheres ........ 17 



4. Polar Bodies 21 



II. Fertilization. 



1 . Entrance of Spermatozoon .......... 21 



2. The Germ Nuclei 22 



3. Egg and Sperm A.sters and Spheres . . . . . . . .23 



4. Approach of Germ Nuclei and Spheres . . , . . . . • .24 



5. Origin of Cleavage Centrosomes 25 



III. Cleavage. 



1. Nuclear Changes during Cleavage 31 



a. Independence of Germ Nuclei ......... 31 



b. Chromatin . . . . • . .36 



c. Separation of Chromosomes and Formation of Daughter Nuclei . . .37 



2. Centrosomes and Central Spindles . 39 



a. Centrosomes 39 



b. Central Spindles . . .41 



3. Polar Rays and Spindle Fibres ; Mid-Bodies 41 



4. Spheres 43 



IV. General Considerations and Comparisons. 



1. The Nucleus during the Cycle of Division 45 



a. Formation of Chromosomal Vesicles ; Growth of Daughter Nuclei . . 45 



b. Chromatic Differentiation ; Solution of Oxychromatin and Nuclear Membrane 47 



c. Escape of Nuclear Substances ; Aster and Spindle Formation . . .48 



d. Chromatic Elimination .......... 51 



2. Centrosomes and Central Spindles . 53 



a. Structure and Metamorphoses ........ 53 



b. Relation of Centrosome to Cell Body and Sphere 54 



c. Relation of Centrosome to Nucleus 55 



d. Comparisons . ■ • , • ■ .56 



e. The Centrosome as a Persistent Cell Organ 61 



f. Homology of the Centrosome 67 



3. Spheres, Idiozome, etc. 70 



4. Archoplasm, Kinoplasm, etc. . . . . . . ' • • .71 



