STUDIES OF AMITOSIS 505 



satisfactory feature in the past studies is that the results of 

 observations have not been subjected to an analysis, so to 

 speak, from a theoretical point of view. We had merely an 

 accumulation of data, which does not yield a clue to the true 

 nature of the phenomenon without being properly treated. 



Before taking up other theories, I wish to say a few words 

 about that of Karpoff ('04). According to this author, amitotic 

 nuclear division may be a phenomenon of purely physical sig- 

 nificance, and his observations are suggestive enough of such an 

 idea. It must not be forgotten, however, that explanations as 

 to the mechanism and as to the biological significance are two 

 different things. We may be able to find the explanation of 

 the method of the process in mechanical theories, but it does 

 not necessarily contradict other theories regarding the 'purpose' 

 of the process. 



The old conception of amitosis as a primitive type of nuclear 

 division derived from protozoan forms, is now universally dis- 

 carded, and so I will not stop to discuss it. 



Nowikoff's ('08, '10) theory that amitosis is a phenomenon of 

 mechanical significance seems to represent the truth, as far as 

 some particular cases are concerned, but its general application 

 is too obviously impossible. He based his theory on the fact 

 that the nuclei located near the surface of cartilage are very 

 much elongated and flattened, due, as he assumes, to mechani- 

 cal necessity from their location, and, since amitosis sets in these 

 elongated nuclei, a certain mechanical stimulus can be considered 

 as underlying amitosis. The fact that this is not the only way 

 in which Nowikoff's data can be interpreted, is suggested in the 

 last section (p. 35). 



Equally unfortunate in its foundation is Jordan's ('13a) 

 theory that amitosis is due to the lack of the centrosome. Many 

 authors have described the presence of the centrosome in various 

 cases of amitosis, and even its apparent activity in the amitotic 

 process (Meves, '94). Jordan's cases, in which the centrosomes 

 are" destroyed in the formation of cilia before amitosis takes 

 place, seem to be good evidence, as far as it goes, in support of 

 the theory, but the observations of Henry ('00), Ikeda ('06) 



