NUCLEAR DIVISION WITHOUT CELL-DIVISION. 1 6/ 



tirely prevented, as above described. In other words, the with- 

 drawal of the electrolytes from the egg in some way prevents the 

 transmission of the division-impulse from the nucleus (which 

 apparently initiates the same) to the body of the cell. 



A similar effect has been observed by J. Loeb l and Norman 2 

 to follow the withdrawal of water from the egg by means of sea- 

 water concentrated by the addition of sodium chloride or mag- 

 nesium chloride ; other instances of nuclear division without 

 cell division have been recorded by various authors (Boveri, 

 Chabry, Driesch, Roux). 3 The fact that this phenomenon is 

 seen in solutions of non-electrolytes is of peculiar interest as 

 indicating the importance of the part played in cell-division by 

 the ions present in the cytoplasm. Nuclear division, on the 

 other hand, is apparently independent of the presence of such 

 ions. 



Not only is cleavage prevented by transfer to non-electrolyte 

 solutions, but a strong tendency to fusjon manifests itself in the 

 blastomeres of eggs transferred during early cleavage stages. 

 This fusion takes place most readily with starfish eggs and in 

 solutions of urea ; glycerine- and sugar-solutions are relatively 

 injurious to the eggs and are accordingly less favorable. 



The following record will illustrate : 



June 2-j, 1902. Starfish eggs, fertilized at 12:25 P. M., were transferred at 2:15 

 P. M. while in the 2-, 4-, and 8- cell stages to m-urea-solution. On examination at 

 3:30 the blastomeres were found in many instances to be completely re-fused, the eggs 

 having apparently reverted to the original unicellular condition. Such eggs form 

 rounded masses of protoplasm each containing several nuclei (which do not fuse) and 

 exhibiting in many cases irregular amceboid projections. 



With eggs of more advanced stages (16- and 32-cell) fusion 

 is rarely so complete as in earlier stages. Adjacent blastomeres, 

 however, gradually flow together, and the resulting compound 

 blastomeres, at first hour-glass-shaped, tend to round off, although 

 slowly and as a rule incompletely. Fig. t is a representation 

 of an egg with partially fused adjacent blastomeres of the 8-cell 



1 Loeb, J. Archi-v fur Entivicklungsniechanik, Bd. 2, 1896, p. 298. 



1 Norman, ibid., Bd. 3, 1897, p. 106. 



3 For a summary of the observations of these authors cf. Korschelt and Heider > 

 Vergleichende Entwicklungsgeschichte, allgemeiner Theil, erste Lieferung, Jena, 

 1902, p. 215. 



