768 CALKINS. 



DESCRIPTION OF PLATE XL. 



Figs. II, 16-19, 21, 22, 24, 26-31, 38 represent nuclei in the process of spore- 

 formation ; Figs, i-io, 12-15, 20, 23, 25, 32-37, 39 are various stages of the 

 vegetative nucleus. Picro-acetic was used for individuals represented in Figs, i, 5, 

 8, 15, 19, 20, 24; sublimate-acetic (weaker solution) for Figs. 6, 7, 10, 13, 17, 18, 21- 

 23, 25, 32-37, 39. Stronger solution for Figs. 26, 27, 29-31, 3S ; Hermann solu- 

 tion for Figs. 9, II, 12, 14, 16, 28; and corrosive sublimate for Figs. 2, 3, 4. 

 The iron haematoxylin was used in all cases save Fig. 10, where the Biondi- 

 Ehrlich mi.\ture was used. Figs, i-g, li-iS, 20, 21 are from preparations in toto ; 

 Figs. 10, 19, 22-3S, from sections, jr^ supposed intra-nuclear centrosome. 



Fig. I. Resting stage of a vegetative nucleus showing 9 karyosomes and 

 granular o.xychromatin. Sphere on the outside of the nuclear membrane presents 

 characteristic granular cortex and hyaline central part. 



Fig. 2. Nucleus showing early stages in fragmentation of the karyosomes. 



Fig. 3. Nucleus showing possible method of karyosome fragmentation. jr = 

 the supposed intra-nuclear centrosome. 



Fig. 4. Later stage in karyosome fragmentation. The granules are gathered 

 in groups, each group representing a previous karyosome. 



Fig. 5. A still later stage in karyosome fragmentation. The sphere appears 

 homogeneous. 



Fig. 6. A nucleus in the so-called " spireme-stage." The chromatin granules 

 are still large, but are arranged in fibers. The supposed centrosome {x) is dis- 

 tinct from the chromatin. 



Fig. 7. Same as Fig. 6. 



Fig. 8. A nucleus in the prophase of division. The achromatin granules are 

 arranged in fibers parallel with the chromosomes. The chromosomes are forming 

 with the thickened ends towards the sphere. The sphere has become more 

 dense, and the hyaline center is disappearing. Some of the karyosomes are not 

 yet fragmented. 



Fig. 9. A prophase of division. The granules are beginning to form fibers, 

 — the chromosomes. The sphere is dividing. Numerous processes stretch out 

 from the sphere into the cytoplasm. These are probably equivalent to astral 

 fibers. 



Fig. 10. The same stage in section. The nucleus is filled with granules which 

 are forming chromosomes. 



Fig. II. Stage of the amphiaster. The chromosomes are all formed and are 

 represented in optical section in the nuclear plate. 



Fig. 12. An abnormal nucleus. The sphere is bent into an acute angle. 

 The nucleus shows elongation in the primary axis before chromosome-formation. 



