289 



The new membranes inside the old nucleus can readily be followed 

 through the nucleus from side to side by careful focussing. 



It is evident that nuclear conditions must be different in the two 

 forms of division. My own observations seem to indicate that ami- 

 tosis is more frequent in connection with rapid nuclear multiplication. 

 In regulation in Tubularia and Corymorpha amitosis appears to be 

 the chief method of division, at least in later stages; in Planaria the 

 periods and regions of most rapid growth show amitosis and no 

 mitosis; in Moniezia, with its enormous power of growth, mitosis is 

 rare; in forms like Pneumonoeces and Arenicola, which produce with 

 relative rapidity large quantities of sexual cells, amitosis appears to be 

 the chief method of division in the primitive stages of these cells; 

 in the dipterous larvae, where the rapidity of development is very 

 great, mitosis rarely appears : in the chick amitosis seems to be more 

 frequent in the rapidly growing regions than in others. 



ZiEGLER ('01) asserts that "die amitotische Kernteilung (vor- 

 zugsweise, vielleicht ausschließlich) bei solchen Kernen vorkommt, welche 

 einem ungewöhnlich intensiven Sekretions- oder Assimilationsprozeß 

 vorstehen". He also attempts to prove that nuclei which divide amito- 

 tically are always of large size, that cell division does not usually 

 follow nuclear division, and that amitosis always indicates the ap- 

 proach of the end of the division series. Later work indicatesthat 

 all of these conclusions are too extreme, but the first appears more 

 nearly to accord with our present knowledge than the others, though 

 even this is not strictly correct, for amitosis may occur in starving 

 tissues. 



It is impossible at this time to review the literature of the sub- 

 ject, but I think it is admitted by all who are familiar with it, that 

 most if not all of the cases recorded, except those occurring under 

 experimental conditions, appear to be associated with relatively rapid 

 nuclear multiplication. While cell division does not always follow 

 amitotic nuclear division there is no doubt that in many cases it does, 

 and while degeneration frequently follows amitosis there are undoubtedy 

 many cases in which it does not. 



II. Suggestions and Interpretations. 

 Since it is evident that the views of Ziegler and Vom Rath do 

 not accord with the facts we must either attempt to arrange and inter- 

 pret the data on some other basis or permit them to remain mere 

 isolated facts without correlation and without general significance. 

 But when we consider the increasing frequency with which the occur- 



Anat. Anz. XXX. Aulsätze. 19 



