2OO 



MAULSBY W. BLACKMAN. 



more spongy (Fig. 9, e]. This continues to become more 

 marked until in a short time one or several projections may be 

 seen extending from its surface (Figs. 10, 11). These granular 

 filaments stain densely and are similar in all respects to the 

 chromatin segments characteristic of the " spireme " stage. They 

 continue to lengthen until when they have attained a certain size 

 they become detached from the karyosphere and lie free in the 

 nuclear space (Figs. 10, II, 12). These segments continue to 

 form until they are exactly equal in number to the threads for- 

 merly seen in the early spermatocytes. 



FlG. II. X I >44 dia. Nucleus of about the same stage as seen in a thinner 

 section. " Spireme" structure of the karyosphere shown. Tetrads in various stages 

 of formation. One centrosome with rays to be seen upon nuclear membrane, the other 

 not included in the section. 



FlG. 12. X I >44 dia. Later stage, showing the unwinding of the last chromosome 

 from the karyosphere, thus again disclosing the accessory chromosome. 



As this process proceeds, the size of the karyosphere de- 

 creases proportionately until finally nothing remains except the 

 body with which the transformation started, the accessory chro- 

 mosome. From this fact alone we might indeed be justified in 

 concluding that the chromosomes are derived from the karyo- 

 sphere, but no such assumption is necessary. Absolute proof of 

 the truth of this statement is at hand. Actual observations of 

 all the stages incident to chromosome formation may easily be 

 made so that it is impossible for the observer to escape the very 

 evident conclusions to be drawn therefrom. Figs. 10 and II 



