Regeneration 189 



Should it be possible that this is more generally the 

 case, e. g. t also in the lens after it has reached a certain 

 size? The conditions limiting growth require further 

 investigation. 



It is hardly necessary to point out that in these cases 

 we are seemingly dealing with cases of the inhibition of 

 growth which cannot be explained by the tyranny of 

 the whole over the parts, and that there must be condi- 

 tions at work other than the mere flow of substances 

 which can cause a cessation of growth. This can be 

 illustrated by certain observations on the egg. 



8. The history of the egg shows a reversible condi- 

 tion of rest and of activity. The primordial egg cell 

 multiplies actively until a large number of eggs are 

 formed in the ovary which may reach into the millions 

 in the case of sea urchins or certain annelids. These 

 cell divisions then stop and the egg goes into the resting 

 stage in which it deposits the reserve material for the 

 development of the embryo. From this condition it 

 can only be called into activity again by the spermato- 

 zoon or the agencies of artificial parthenogenesis. 



It seemed of interest to find out whether or not the 

 development of the egg may be reversed once more 

 after it has been activated. From all that has been said 

 in the chapter on artificial parthenogenesis, such a 

 reversal should take place in the cortical layer. The 

 result of these experiments seems to be that if a complete 

 destruction or change in the cortical layer has once 



