626 L- R. ^'ary, 



the appearence of rather fine, densely staining-, granules which are 

 scattered throughout the "central mass". (Fig. 17). These granules 

 increase in size, (Fig-. 18), until thej^ fill the central mass. Where 

 the granules come in contact they fuse with one another, to form 

 a continuous thread. (Figs. 18, 19 and 20). When they first become 

 arranged to form the spireme thread the latter lies coiled up within 

 the central mass, which has not as yet increased in size since the 

 time of the condensation of the contents of the nucleus. 



When the spireme becomes definitely established as a thread, 

 there ensues a period of rearrangement of the nuclear contents. The 

 spireme thread grows at first faster than the diifusion of the "central 

 mass" takes place so that at a number of points the chromatic thread 

 forms protuberances on the surface of the latter, (Fig. 19). In later 

 stages the rearrangement of the less chromatic part of the nuclear 

 contents goes ahead of the growth of the spireme thread, as shown 

 in Fig. 20. This rearrangement of the nucleoplasm follows apparently 

 the same lines, traversed in an opposite direction, when it was taken 

 up by the caryosome. Each "suspensory sti-and" becomes separated 

 into its two component parts, (Figs. 18 and 19), and these walls 

 become further and further separated with the expansion of the 

 "central mass". In a stage as shown in Fig. 20, the nuclear contents 

 have become extended to fill the entire cavity inside the nuclear 

 membrane, while there is yet a more darkly staining area about 

 the spireme thread. In later stages when the chromosomes have 

 become differentiated, and are being arranged to form the equatorial 

 plate, the whole of the nucleoplasm has a uniformly light staining 

 reaction. 



The spireme thread in its later growth comes to fill the entire 

 nucleus (Fig. 23). Sometimes before the redistribution of the 

 nucleoplasm is completed, the spireme thread becomes constricted at 

 a number of points so that it appears like a chain of very long 

 beads. The characteristic shape of the component granules (Figs. 

 24 and 25) serves to distinguish such a stage from one in which 

 the spireme thread is being formed by the fusion of the granules 

 as in Fig. 17. 



The constrictions separating the chromosomes become deeper 

 until the latter are sharply marked off from one another, (Fig. 24). 

 Later the chromosomes become separated from one another by a 

 little distance, but for some time the}^ remain connected together by 

 thin strands of achromatic material (Fig. 25). 



