1922] Kofoid-Swezij: Mitosis in Endamorha dyseideriae 



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A third ei'iterion exists in the number of ehromosomes. The 

 number of chromosomes in man appears to be either 24 or 48, or pos- 

 siblj' both, the former being the diploid and the latter, the tetraploid 

 condition. Guyer (1910, 1914) reported 22, but Montgomery (1912) 

 and Wieman (1917) raised the number to 24. However, double this 

 number have been reported by Evans (1918, 1921) and Painter 

 (1921) who suggest 45 to 48. The finding of 47 chromosomes by 

 Winiwarter (1917) in tlie testis suggests the possibility that there 

 may be 47 in the male and 48 in the female in the tetraploid phase, 

 and, by inference, in the diploid phase 23 and 24. 



We have found (Kofoid and Swezj-, 1921) 8 chromosomes in 

 Councilmania la^fleuri, and 6 (see also Swezy, 1922, in press) in Eiida- 

 nioeha coli, and probably 6 (not less than 5 nor more than 7) in 

 Endanioeha dyscnterlac. The number of chromosomes in the dividing 

 cells which we interpret as dividing amoebae is not 24, much less 48. 

 It is at the most a small number (fig. 6), probably 6. The number 

 in the dividing human cells observed by us in lymph glands of 

 Hodgkin's disease (figs. 1 and 2) is many more than 6. The chromo- 

 somes are so crowded in the equatorial plate (fig. 1) or so overlie 

 each other, especially at the margins of the divided equatorial plate 

 in lateral view, that the exact number can not be ascertained with 

 certainty. We have not yet found a polar view in which the prac- 

 ticability of counting will be enhanced. The individual chromosomes 

 are indicated by the projecting lobes representing their free ends. 

 The number of these free ends on either side (fig. 2) or of elbows on 

 the polar side of each group may be estimated in the mast favorable 

 region, namelj-, a sector of 90° on one surface. The number in our 

 sections appears to be not less than 24, and not the tetraploid (?) 48. 

 It is certainly not 6. In view of the general acceptance by cytologists 

 of the view that the somatic chromosome number is both constant and 

 characteristic, we are constrained to believe that this criterion is valid 

 and critical to determine the non-human and the amoebic identity of 

 these cells. 



The chromosomes of the human cells are also larger and propor- 

 tionately longer than those of the amoebae. They are consistently so 

 in all the mitotic figures at the metaphase or near it of the amoebae 

 which we have been able to detect, and we find no evidence in our 

 material which connects these types of mitosis with any observed form 

 of degenerating human cells. They appear to be normal parasitic 

 amoeba in the normal phases of mitosis. 



