604 THE PHASE OF THE NUCLEUS KNOWN AS SYNAPSIS. 



Fig. 10. The nuclear cavity has enlarged to nearly twice its original size, but there is no evidence of 

 contraction of the chromatin. 



Fig. 11. The nuclear cavity has enlarged still more. The threads of the spireme are beginning to loosen 

 *ud project into the clear area of the nuclear sap. The double nature of the threads may be clearly seen. 



Fig. 12. The same, but a later condition of the loosening of the spireme threads. 



Fig. 13. The same. The nuclear cavity has enlarged still more. 



Fig. 14. The same, from a section that has not been cut in a median plane through the chromatin mass. 



Fig. 15. A further stage in the development of the spireme. The double threads are much more sharply 

 defined and their ends are clearly visible. 



Fig. 16. The nuclear cavity is now more than twice its original size. 



Fig. 17. The rounding off of the corners of the mother-cells indicating the presence of an intercellular 

 space. The distension of the nuclear cavity is directed towards this intercellular space, leaving the chromatin 

 behind at the opposite side. 



Fig. 18. A more striking example of the same. 



Fig. 19. The spireme threads now show the short segments or "chromomeres." 



Fig. 20. This stage is an excellent example to show the distension of growing nuclear cavity towards the 

 intercellular space. That is, it extends in the line of least resistance leaving the spireme behind. 



Fig. 21. The loosening of the spireme becomes more evident. 



Fig. 22. Another stage of the same. 



Fig. 23. The spireme threads projecting and extending into the large clear area of the nuclear sap. 



Fig. 24. Another stage of the same. 



Fig. 25. The spireme threads are now nearly uniformly distributed through the enlarged nuclear cavity. 



Fig. 26. The chromosomes may now be identified and followed from end to end. The enlarged nuclear 

 cavity has resumed its spherical form owing to the fact that the mother-cells are practically free from one 

 another. 



Fig. 27. This stage clearly shows the diploid number of chromosomes, proving that reduction could not 

 possibly have taken place in any of the previous stages. 



Fig. 28. A much later stage, showing the chromosomes consorting in pairs. 



