SOME EXPERIMENTS ON CELL-DIVISION. 



275 



rated from one chromosomal plate at an anaphase and the daughter nucleus 

 was formed independent of the aster. It is quite probable, however, that a 

 portion of old centrosome was left around the karyomeres, but none the 

 less conclusive that the growth of the daughter nucleus have been ac- 

 complished widely separated from the new aster. 



In closing I wish to express my thanks to Prof. E. B. Wilson, who 

 .kindly looked over the manuscript of this paper. 



SUMMARY. 



The conclusions arrived at from the fourteen cases mentioned in the 

 present paper are as follows: — 



(1) An enucleated fragment with the aster shows a disturbance of surface 

 tension at the end farthest from the aster. 



(2) An enucleated fragment without the aster often shows a division 

 activity and in some cases it is completely divided into two. 



(3) A mass of cytoplasm has in itself, or acquires under certain condi- 

 tions, the power of dividing itself with the aid of neither rays nor 

 centrosomes, 



(4) Cleavage goes on normally even after one of the centres is cut off at 

 an anaphase. 



(5) After the cleavage plane is fixed i. e., after the formation of the 

 diasteme, the cleavage furrows proceeds normally notwithstanding the 

 removal of a portion of cytoplasm. 



(6) Cleavage between two asters with a spindle takes place perpendicular 

 to the middle point of the spindle, irrespective of the position of the 

 asters. 



(7) One-sided constriction of the first division occur abnormally outside 

 the coelenterates and Petromyzon. 



(8) The karyomeres may fuse and form a daughter nucleus even when 

 the chromosomes have been separated from the aster. 



Zool. Laboratory, Tokyo Imp. Univ. 

 Dec. 3 1907. 



