RELATION BETWEEN AMITOSIS AND MITOSIS. 171 



of new nucleoli in widely separated regions of the nucleus and 

 the difference in tingibility of the two parts of a dividing nucleus, 

 which are often observed in Moniezia, indicate the existence of a 

 certain degree of physiological independence before separation of 

 the parts. 



If this interpretation of the visible phenomena is correct it ap- 

 pears probable that mitosis is associated with certain cyclical proc- 

 esses, in the nucleus and amitosis with acyclical or orthodromic 

 processes. In other words, in order to divide mitotically the 

 nucleus must be in a condition approximating equilibrium between 

 intake of material and functional transformation. If the stimulus 

 to growth is so strong that the nucleus is forced far from a con- 

 dition of equilibrium amitotic division may occur. Of course in 

 all cases where the demand exceeds the supply the actual rate of 

 growth or division is determined not by the intensity of the 

 stimulus but by material available. According to my sugges- 

 tions, it is not rapidity of growth or division Avhich determines or 

 influences the form of division, but rather the relation between the 

 stimulus to growth and the intake of material. Division itself is 

 probably an incidental result of growth. These suggestions are 

 of course merely provisional, being scarcely more than surmises, 

 but they may perhaps serve as a working hypothesis for future 

 investigation of the problem. 



But whatever value the future may assign to these suggestions, 

 the facts now known regarding the occurrence of amitosis seem 

 to be in accord with this hypothesis, as will be clear from a brief 

 consideration. 1 Most of the earlier observers agree in the con- 

 clusion that amitosis is characteristic of regions of extreme phy- 

 siological activity connected with assimilation, secretion, etc. 

 (Ziegler, '91 ; Ziegler and Vom Rath, '91 ; Vom Rath, '95, etc.). 

 More recent observations of others and myself some of which are 

 briefly mentioned in my earlier paper (Child, 'ojc) show that 

 amitosis is of frequent occurrence in regulatory growth, which is 

 much more rapid than normal growth. It is also the typical 

 form of division in the imaginal organogeny of certain diptera and 

 very probably of many insects. Here, likewise, the growth is 



1 More extended discussion of the bibliography is postponed until adduional data 

 have been recorded. 



