28O BERTRAM G. SMITH. 



EXPLANATION OF PLATE VI. 



Cryptobranchus allgeheniensis. 



FIG. 27. Horizontal section through a nucleus in a late prophase of the second 

 cleavage mitosis. A small portion of each group of chromosomes is left in each 

 of the adjacent sections. The axis of the spindle lies in a direction nearly parallel 

 to the plane -of first cleavage. Fixed with bichromate-acetic-formalin; stained 

 with borax-carmine Lyons-blue picric-acid. X 400. 



FIG. 28. Horizontal section through one of the daughter-nuclei in a late stage 

 (early telophase) of a second cleavage mitosis. Orientation as in the preceding 

 figure; the second cleavage furrow is not yet formed. Fixed in Zenker's fluid; 

 stained with iron-hsematoxylin. X 400. 



FIG. 29. Horizontal section through one of the daughter-nuclei of a second 

 cleavage mitosis; early resting stage. Part of the nucleus is left in an adjacent 

 section where it is likewise distinctly double. The plane of apposition of the two 

 nuclear vesicles is parallel to the first cleavage furrow, and at right angles to the 

 second cleavage furrow which is beginning to form. Bichromate-acetic-formalin 

 fixation; stained with iron-haematoxylin. X 400. 



FIG. 30. Horizontal section through one of the daughter-nuclei of a second 

 cleavage mitosis; resting stage. A portion of the nucleus is left in each of the 

 adjacent sections where it is likewise distinctly double. The plane of apposition 

 of the two nuclear vesicles is parallel to the plane of first cleavage, and at right 

 angles to the beginning second cleavage furrow. Bichromate-acetic-formalin 

 fixation; stained with borax-carmine Lyons-blue picric-acid. X 400. 



FIG. 31. Vertical section through one of the daughter-nuclei of a second cleavage 

 mitosis; resting stage. The section is taken parallel to the plane of the second 

 cleavage furrow which has just begun to form. Part of the nucleus is left in an 

 adjacent section, where it is likewise distinctly double. Bichromate-acetic-formalin 

 fixation; stained with borax-carmine Lyons-blue picric-acid. X 400. 



FIG. 32. Horizontal section through a nucleus rotating into position for the 

 third cleavage mitosis; almost the entire nucleus is confined to this section. The 

 second cleavage furrows are present and extend nearly to the equator of the egg. 

 Bichromate-acetic-formalin fixation; stained with borax-carmine Lyons-blue picric- 

 acid. X 400. 



