Vol. XIV. March, igo8. No. 



BIOLOGICAL BULLETIN 



A STATISTICAL STUDY OF MITOSIS AND AMITO- 



SIS IN THE ENTODERM OF FASCIOLARIA 



TULIPA, VAR. DISTANS. 1 



O. C. GLASER. 



Introduction. 



Remak's ('41) diagrammatic schema of nuclear and cell divi- 

 sion was banished from the field of normal biology by the cyto- 

 logical work of the decade following its proposal. Since that 

 time it has ever remained heresy to associate amitosis of any sort 

 with anything else than cellular senescence, or a high grade of 

 specialization, or intense metabolic activity. " When once a cell 

 has undergone amitotic division it has received its death war- 

 rant," wrote vom Rath ('91), and although this assertion is now 

 acknowledged to be extreme, its spirit is nevertheless still so 

 firmly engrafted on biological literature and thought that the un- 

 canonical facts claimed by Pfeffer ('99) to obtain under experi- 

 mental conditions in Spirogyra, and by M eves ('91) under natural 

 conditions in the testis of the salamander have been regarded 

 more as anomalies than as contributions to our knowledge of cell 

 division. Quite recently however Child ('04 ; '07 I., II., III., 

 IV., V., VI.; 'oya) as the result of his very careful work on the 

 cestode Moniezia, and his more or less exploratory observations 

 on representatives of almost every phylum in the animal king- 

 dom, has forced upon cytologists so many instances in which 

 amitosis seems to occur in normal and healthy tissues, that the 

 significance of what he found demands serious consideration. 

 Appeal to inadequate technical methods, to senescence, to spec- 

 ialization, or to pathology are insufficient. Wheeler ('89) and 



1 Contributions from the Zoological Laboratory, University of Michigan, No. 114. 



219 



