15U 



0SM0-RE6ULATI0N 



I -10 - 



distilled water 



tap water 



standard solution 



frog Ringer _...■• 



10 15 



hour6 



23 



The relative size of unfertilized 

 eggs of R. plplens, expressed as 

 percentage Increase or decrease 

 from the Initial size (Indicated 

 by 100) , after exposure to salt 

 solutions of varying osmotic 

 pressure. 21 to 24°C. 



Viscosity of the 

 cytoplasm 



Elasticity of the 

 surface coat 



Surface sticky 

 to glass 



DIS- 

 TILLED 

 WATBR 



Effects of various osmotic pressure 



upon amphibian cells up to the Aggregation of 



neurula stage. pH 7.6 to 8.2. uncoated cells 



Cleavage in isolated 

 blastome'res 



Isolated cells 

 die after 



Cells swell 

 Cells shrink 

 Embryo gastrulates 

 Neuralplate closes 



< 



+ + + 



10- 

 15 min. 



+ 

 + 



PHTSIOLOOICAL SALT SOLUTIONS 



0.20% 



< 1 < 



1 



10- 

 15 min. 



+ 



+ 

 + 



+ + -1- 



( + ) 



20- 

 60 min. 



+ 

 + 



0.38% 0.57% j 0.6S% I 0.76% 



Hypotonic 



Neurulae of Trlturus torosus exposed 

 (a) to Ringer, (b) to standard solu- 

 tion, (c) to tap water display vary- 

 ing degrees of retarded development 

 and lose mesectoderm cells. 



From Holtfreter, I9U5. Jour. Exp. Zool. 95:251 



