282 BERTRAM G. SMITH. 



EXPLANATION OF PLATE VII. 



Cryptobranchus allegheniensis. 



FIG. 33. Horizontal section through a resting nucleus in position for the third 

 cleavage mitosis. The plane of apposition of the two nuclear vesicles is nearly 

 parallel to the second cleavage furrows. A considerable part of the nucleus is 

 left in an adjacent section, where it is likewise distinctly double. Fixed with 

 bichromate-acetic-formalin; stained with borax-carmine Lyons-blue picric-acid. 

 X 400. 



FIG. 34. Horizontal section through a nucleus in position for the third cleavage 

 mitosis. A line connecting the two asters is nearly parallel to the second cleavage 

 furrow. Part of the nucleus is left in an adjacent section, where it is likewise 

 distinctly double. Fixed with bichromate-acetic-formalin; stained with borax- 

 carmine Lyons-blue picric-acid. X 400. 



FIG. 35. Vertical section through a nucleus entering upon the third cleavage 

 mitosis. Part of the nucleus is left in each of the adjacent sections, where it is 

 likewise distinctly double. Fixed with bichromate-acetic-formalin; stained with 

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



FIG. 36. Horizontal section through a nucleus in the late prophase of the third 

 cleavage mitosis. A line connecting the two asters extends nearly at right angles 

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

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



FIG. 37. Horizontal section through a daughter-nucleus of a third cleavage 

 mitosis. The two nuclear vesicles remain almost in the position in which they 

 were formed, but two asters are present and these have taken up a position prepara- 

 tory to the fourth cleavage mitosis. A line connecting the two asters extends in a 

 direction almost parallel to the adjacent newly-formed third cleavage furrow 

 which is vertical and intersects a second furrow almost at right angles. Fixed in 

 bichromate-acetic-formalin; stained with borax-carmine Lyons-blue picric-acid. 

 X 400. 



FIG. 38. Horizontal section through a nucleus in position for the fourth cleavage 

 mitosis. A line connecting the two asters extends parallel to the adjacent third 

 cleavage furrow and almost parallel to the first furrow. Fixed in bichromate- 

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



