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Ziegler und Vom Rath zu teil wurde". And further: "Daß jedoch 

 die allgemeine Begründung des Standpunktes von Flemming Richtiges 

 in sich birgt, kann ja nicht bestritten werden, da das Auftreten der 

 Amitose in der überwiegenden Mehrzahl entweder auf pathologische 

 Gewebe oder auf solche von nur sehr geringer Lebensdauer und ohne 

 wirkliche Organisationsfähigkeit beschränkt bleibt." He concludes, 

 however, that we must admit with Pfeffer "die Möglichkeit einer 

 physiologischen Vertretbarkeit beider Kernteilungsmodi". 



It is perhaps not surprising that amitosis should have failed to 

 attract the attention which has been devoted to mitosis. The con- 

 spicuous and complex character of the latter, its apparently universal 

 occurrence in maturation and early development and its wide occurrence 

 elsewhere have all contributed to direct attention to it. Moreover, 

 mitosis presents a most favorable field for the development of hypo- 

 thesis and theory and has certainly received no less attention on this 

 account. Amitosis is often much more difficult to discover than mitosis 

 and may easily be overlooked in small nuclei. Its occurrence can be 

 regarded as certain only when the critical stages immediately preceding 

 and immediately following separation of the daughter-nuclei are ob- 

 served. The fact that so many of the cases already described have been 

 found in large and conspicuous nuclei is doubtless explained by the 

 difficulties of observation. Moreover, the attention of cytologists has 

 of late years been confined very largely to growth, maturation and 

 fertilization in the germ cells. Embryologists engaged in the study of 

 organogeny have commonly paid but little attention to the details of 

 structure in nuclei, often minute and crowded together in such manner 

 as to render close examination extremely difficult, and ordinary histo- 

 logical methods are in large measure unsuitable for such purposes. 

 The presence of mitosis in growing tissues has generally been accepted 

 as proof that mitosis is the characteristic method of division, but in 

 numerous cases the infrequency or absence of mitosis has been noted. 



The chief purpose of the present paper is to show that pheno- 

 mena which present all the characteristics of amitotic nuclear division 

 are of frequent occurrence in the normal development of many forms. 

 My observations on Moniezia and Planaria are more extensive 

 than those on other forms and will appear in full elsewhere. In a 

 number of cases no extensive examination and comparison of different 

 stages has yet been made in order to determine the relative frequency 

 of the phenomena described. Such comparative investigation, however, 

 offers a most interesting field. 



All figures accompanying the present paper are camera drawings 



