A STATISTICAL STUDY OF MITOSIS AND AMITOSIS. 233 



the results are actually based on three larvae of the cannibal 

 period, and on four of the post-cannibal period though many 

 others were used for comparison. 



A final difficulty not at all peculiar to Fasciolaria, but to be 

 expected wherever amitosis occurs, is this : How can one tell that 

 what seems to be an amitotic division is really such ? Since in 

 amitosis there occur none of the striking changes that character- 

 ize mitosis, it is, as Hertwig ('98) has pointed out, impossible to 

 be sure that direct divisions are going on unless one can find all 

 possible stages in the process. The mere lobulation of nuclei is 

 not sufficient. I believe that Fig. 7 is an answer to the criticism 

 which neglect of Hertwig's warning might justify. Of course, 

 many of the nuclei there pictured would not have been included 

 in the same plate with those which I cannot doubt are amitotic, 

 had I not found the latter. Given stages however which it is im- 

 possible to interpret in any other way, it seems mere pedantry 

 to exclude all of the others which taken by themselves, would 

 either not be convincing, or to the casual observer, might not 

 even suggest amitosis. Had it been impossible for instance to 

 find all of the intermediate stages between a resting nucleus and 

 a late metaphase, I doubt very much whether anyone totally 

 ignorant of the process of mitosis would be able to assert that the 

 latter stage had been derived from the former. The initial and 

 final conditions however are safely interpreted in terms of the 

 intermediate stages that have been found, and every step in the 

 process is illuminated by every other step. However, I have 

 chosen to err on the safe side, and while Fig. 7 includes all of 

 the different nuclear forms met with, in the actual counts only 

 nuclei like 6, 7, 8, 9, 10, 11, 12 and 13, were included. None 

 of the nests, such as 16 and 17, were counted, nor the elongated 

 forms, like 18 and 19, from which the nests may have been de- 

 rived. Even nuclei as close together as 14 were not included, 

 nor such as 1 5 in which the cell boundary enclosing them could, 

 as is sometimes the case, be distinctly traced. 



Summing up the effects which all of these difficulties and their 

 evasion have on the final result, I think it may be justly said that 

 the incompleteness of many of the sections is without signifi- 

 cance ; that the complete elimination of the temporary cells 



