A STATISTICAL STUDY OF MITOSIS AND AMITOSIS. 235 



involves also the elimination of a considerable number of per- 

 manent ones ; and that the fact that mitoses can be cut in more 

 planes, and also into a greater number of sections in any plane, 

 than amitoses, and still reveal their true nature, increases greatly 

 the percentage of indirect divisions in the determinations of the 

 relative frequencies of these two forms of division. The fact that 

 amitoses are much harder to recognize than mitoses, and that I 

 counted as direct divisions only those that seemed to me unques- 

 tionable cases, also helps to increase the relative frequency of 

 mitosis in the final determinations. It follows therefore that the 

 methods employed give a maximum of mitoses and a minimum 

 of the process that I interpret as amitosis. 



The Relative Frequency of Mitosis and Amitosis. 



The main results of my work are graphically illustrated by 

 Fig. 9. There are arranged in tabular form, outline drawings of 

 larvae in the stages of development used, and on a line with each 

 one are the number of sections on which the determinations are 

 based ; a statement concerning the condition of the entoderm ; 

 the number of nuclei actually counted ; the number of mitotic 

 divisions found ; the number of amitoses registered ; and the 

 number of cells either actually found in the transverse planes 

 indicated on the drawings, or inferred to be present there from 

 evidence which will be given in detail for each case in which 

 inference replaces actual counting. 



Analysis of this table reveals several interesting facts. In 

 stage I. for example, there is a higher percentage of mitoses, and 

 of course a lower percentage of resting nuclei than in any of the 

 other stages. Three years ago when I had worked out the 

 relations between direct and indirect nuclear division in the ento- 

 derm, I had come to the conclusion that in the early stages the 

 divisions in this tissue were predominantly mitotic whereas in the 

 later stages the reverse was true. My notes in some way were 

 -lost but on repetition the same result, as the table shows, 

 appeared. I thought at that time that the numerous amitoses 

 in the later stages were connected entirely with digestion, and 

 were of no significance in the formation of the definitive entoderm. 

 Although not published in any journal I expressed this view in a 



