7/2 CALKINS. 



DESCRIPTION OF PLATE XLII. 



Fig. 26. Transverse section showing the double nature of the chromosomes 

 and compact arrangement of the proximal ends. 



Fig. 27. Similar section showing one chromosome {A) beginning to split at 

 the proximal end. 



Fig. 28. Later stage. Mantle-fibers connect double centrosomes with the 

 dividing chromosomes. Two separate bundles of daughter-chromosomes can 

 already be made out. 



Fig. 29. Division of chromosomes is carried still farther ; the distal ends 

 are not yet divided. In both figures the characteristic crossed appearance of this 

 stage is plainly visible. The nuclear membrane persists except where mantle- 

 fibers connect centrosome and chromosomes. 



Fig. 30. A later stage in chromosome division. The distal ends are now- 

 separated. The nuclear membrane has reappeared between the central-spindle 

 and the chromosomes. 



Fig. 31. Horizontal section of similar stage. The central-spindle lies through 

 the middle of the figure, the nuclear membrane is intact except at the poles. 

 This is about the same stage represented in Fig. 17, and would represent a section 

 cut in the plane of the paper. 



Fig. 32. Prophase of vegetative division showing slight undulation in the 

 membrane below the sphere, a hyaline space below the undulation, and two dis- 

 tinct granules in the hyaline space. 



Fig. 33. Prophase of vegetative division showing very marked undulation of 

 the membrane below the sphere, a distinct hyaline sphere, and again two granules 

 within the space. 



Fig. 34. Prophase of vegetative division. A distinct depression is now 

 formed at the point where undulations appeared in the other cases. The two 

 distinct granules are now seen in the space just outside of this depression. 



Fig. 35. Prophase of vegetative division. The undulations are very marked 

 in the region of the sphere, and are not found elsewhere. The two distinct granules 

 are outside of the membrane. 



Fig. 36. A similar stage. The two granules now lie in the sphere, the chro- 

 matin is in the so-called spireme-stage, and chromosomes are forming. 



Fig. 37. The two granules are now very distinct and lie in the sphere. The 

 nucleus is elongated in the primary axis, but the chromatin is still widely dis- 

 tributed. 



Fig. 38. Section through primary axis of a daughter-nucleus in about the 

 same stage as that shown in Fig. 18. The chromosomes are double, the mantle- 

 fibers are distinctly granular, and the centrosome is double. The sphere has not 

 yet divided. 



Fig. 39. Late anaphase in vegetative division. The nuclear membrane is not 

 yet reformed, the mantle-fibers are disappearing, and the chromosomes are disin- 

 tegrating. 



