FUSION OF BLASTOMERES AND NUCLEAR DIVI- 

 SION WITHOUT CELL-DIVISION IN SOLU- 

 TIONS OF NON-ELECTROLYTES. 



RALPH S. LILLIE, 

 UNIVERSITY OF NEBRASKA. 



I. INTRODUCTORY. 



Blastomeres derived from the cleavage of a single egg-cell 

 have not infrequently been observed to reunite or flow together 

 under various abnormal conditions, producing an apparent re- 

 versal of the normal cleavage-process. Thus Dreisch ' in 1893 

 observed a refusion of blastomeres in the 4-cell stage of 

 Echinus as a result of exposure to temperatures higher than the 

 normal (26 degrees). In 1894 Graf 2 found that compression of 

 Arbacia eggs in early stages (16 to 32 cells) also led to a fusion 

 of adjacent cells and even in several instances to a complete re- 

 Aversion from one cleavage stage to the stage immediately pre- 

 ceding (c. g., from 1 6 cells to 8 cells). In 1896 J. Loeb 3 

 observed similar phenomena in Ctenolabrus eggs deprived of 

 oxygen ; he ascribed the effect to a liquefaction of the cell-mem- 

 brane and a consequent flowing together of the protoplasm of 

 adjacent cells. Phenomena of a somewhat different though 

 closely related order have also been observed from time to time. 

 Ziegler, 4 while studying the cleavage of enucleated blastomeres, 

 observed that these cells frequently underwent only partial divi- 

 sion, the cleavage-furrow forming and subsequently disappearing ; 

 and similar "abortive attempts at division " have been described 

 by other authors. 5 In such instances the cleavage-process appears 

 at first to proceed normally, but it remains incomplete and the 

 cell resumes its original form when the impulse to division 

 ceases. 



1 Driesch, Zeitschrift fur wissenschaftliche Zoologie, 55> I ^93, p. 10. 



2 Graf, Zoologischer Anzeiger, 17, 1894, p. 424. 



3 f. Loeb, Archiv fitr die gesammte Physiologic, 62, 1896, p 249. 



4 Ziegler, Archiv fiir Entivicklungsrnechanik, 6, 1898, p. 282. 



6 Cf. Wilson, Archiv filr Entiuicklungsmechanik, 12, 1901, p. 529. 



164 



