758 CALKINS. [Vol. XV. 



8. While the chromosomes are forming, the nuclear mem- 

 brane disappears from between the chromosomes and the cen- 

 tral-spindle. This leaves the chromosomes in contact with 

 the spindle-fibers. 



9. The central-spindle fibers have no connection with the 

 chromosomes, but pass without interruption from pole to pole. 

 The chromosomes are connected with the spheres by another 

 set of fibers, — the mantle-fibers, — which pass from centro- 

 somes in the spheres to the ends of the chromosomes. 



10. The nucleus, during the anaphase, elongates in the 

 direction of the central-spindle. The chromosomes are pulled 

 apart, the final division taking place at the distal end of each. 

 As they separate still more, they form two sets of oppositely- 

 directed striations in the nucleus, and the daughter-chromo- 

 somes again thicken at the proximal ends. 



11. The nucleus, finally, divides in the center, often with a 

 very large connecting-piece between the daughter-nuclei. The 

 furrow is obliterated, the nuclear membrane reforms, and the 

 nucleus rounds out. The sphere loses its densely compact 

 appearance and becomes more expanded, although its granular 

 structure is retained. 



12. In spore-forming divisions the nuclei do not return to 

 the resting state. The daughter-spheres divide and form sec- 

 ondary or tertiary, etc., amphiasters ; the daughter-chromo- 

 somes form the nuclear plate of the next mitosis without 

 change ; and split again longitudinally. This process is 

 repeated eight or nine times. 



13. A centrosome is always found in the sphere during 

 metaphase and anaphase stages as the focal point of the man- 

 tle-fibers, but is not found during resting stages. It divides in 

 the early anaphase in anticipation of the next mitosis. 



14. The centrosome, possibly, comes from the nucleus, 

 where, during the resting stages, a small, deeply staining 

 granule can be easily distinguished from the chromatin. This 

 granule disappears during the early stages of chromosome- 

 formation. At the same period the nuclear membrane, just 

 below the sphere, shows distinct undulations, or wrinkles, 

 which form a clear space below the membrane. In numerous 



