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Balls .— The Mechanism of Nuclear Division. 
Diagram of the Nuclear Mechanism. 
Diagrams made on the assumption that the fusion of the gamete nuclei is delayed until synapsis. 
If this fusion takes place at fertilization we have a simpler scheme. Fig. i then resembles Fig. 2, 
except in the chromosomes, and Figs. 12-15 are simpler. 
1. Somatic nucleus with two chromosomes, each in its own thread-ring : i.e. one chromosome 
and ring from each gamete. 
2. Synapsis ; fusion of the rings, bivalent chromosomes. 
First reduction division:—3. Prophase; 4. Metaphase; 5. Anaphase; and 6. Telophase. 
Second reduction division :—7. Prophase; 8. Metaphase ; and 9. Telophase, with one repre¬ 
sented as having cross-bridles. 
10. Gamete nucleus ; chromatic substance distributed through thread-ring and bridles. 
11. Gamete nuclei approaching in fertilization. 
12. First division of zygote : chromosomes dividing. 
13. „ „ prophase ) 
14. ,, ,, metaphase > Any somatic division. 
15. ,, ,, telophase ) 
