IIO E. G. SPAULDING. 



Such liquefaction phenomena do not of course in every case 

 mean, nor are they the whole of cell division, neither do they in any 

 case account for this except by also taking into consideration the 

 chemical organization previously referred to. But that such a 

 liquefaction takes place during segmentation is evidenced also by 

 (l) the greater susceptibility of the fertilized egg at that time to 

 ether, HC1, KG, etc., results obtained by the author in work 

 on Arbacia, and an account of which will appear in a subse- 

 quent paper, and (2) by the results obtained by Lyon this sum- 

 mer, which indicated a rhythm in the use of oxygen and the 

 giving off of CO 9 by the egg. The last is at the maximum 

 during segmentation, which accordingly points to a greater 

 splitting of molecules at that time and a consequent increase in 

 osmotic pressure and absorption of water. 



Another theoretically possible direct cause of a decreased ten- 

 sion would be the presence at the surface of the egg of like 

 electrical charges. But as this concerns our own experimental 

 work \VG postpone its consideration until further on. 



A. fourth possible method here would be that of mechanical 

 agitation, by means of which the attracting forces of the mem- 

 brane of the cell would be lessened ; for in a physical experiment, 

 at least, the form is charged, the average tension therefore de- 

 creased by mechanical work done from without. By analogy 

 this may hold good of the egg, and to it corresponds the method 

 of agitation used on starfish eggs. Its efficacy may be further ex- 

 plained if it is recalled that agitation may also result in a molecular 

 splitting and consequent increase in pressure. As this com- 

 pletes the possible cases under this class of methods we may 

 pass to the consideration of the other class. 



B. Factors Directly Affecting the Osmotic Pressure. 

 We are here concerned with the establishment of a potential 

 difference in the direction of osmotic pressure surface tension 

 by directly raising the former. Two classes of theoretically 

 possible methods for doing this are to be considered, by bring- 

 ing about (i) analytic chemical changes in the solute and (2) 

 physical changes of pressure. 



