424 



B. WAGE CARLIER 



tecedent substance to zymogen, I believe, which causes such exhaustion of 

 the nuclei and which must necessarily cease to be produced the moment the 

 nuclei hâve reached a certain stage of exhaustion. The convertion into zy- 

 mogen appears to be much less exhaustive, but until the nucleus has comple- 

 tely recovered from its efforts no more prezymogen can be produced and 

 further the cell does not part with its stone of zymogen until the nucleus is 

 in a fit state to undertake the production of a new supply of prezymogen, 

 the manufacture of which is begun as soon as sécrétion commences to be 

 poured out by the cell. 



With regard to the nature of nucleoli I hâve become convinced by my 

 work on thèse and other cells that in the main they consist of effete material 

 produced by the vital activity of the cell, and that it is retained for a time 

 within the nucleus untill its further accumulation there would prove detri- 

 mental to the work and well-being of the nucleus ; it is then removed in 

 the most rapid manner possible by the simple process of extrusion into the 

 protoplasm, where it breaks down and disappears. 



Its passage through the nuclear wall leaves no wound, the nuclear wall 

 closing behind it without showing any visible trace of its passage. 



Further the greater the activity of the cell the greater is the rate ot 

 formation of this effete material and the more frequently is the voiding 

 process gone through. 



The précipitation of lanthanin in the form of colourable granules is also 

 of use, though artiticial, as it gives an indication of the changes going in the 

 nuclear juice during activity and by its change in reaction marks a change 

 in the nature of that juice especially manifested during the early stages of 

 repair of the nucleus increasing in quantity and staining as it does first dark 

 blue, before finally becoming almost neutral as in the resting condition. 



The fréquent mitosis exhibited by thèse cells is also an interesting fact. 

 The chromosomes number 24. 



