1905.] Occurrence of Heterotypical Mitoses in Cancer. 231 



cell, because they are only attached to one or other attraction sphere, and 

 also by " casting out of chromatin." " Casting out of chromatin " is merely 

 an exaggeration of what occurs in asymmetrical mitosis ; in it some chromo- 

 somes remain unattached to either attraction-sphere, and therefore fail to be 

 included in either daughter nucleus. Krompecher* and we ourselvesf have 

 shown that multipolar mitoses may also lead to a diminution in the number 

 of chromosomes. We stated that nuclei with diminished and half the 

 somatic number of chromosomes occur without it being possible to determine 

 whether the diminution has been effected by asymmetrical mitosis, casting 

 out of chromatin, multipolar or heterotypical mitosis. 



We have given our reasons for now believing that the mitoses we formerly 

 assumed confirmed the occurrence of a heterotypical reducing division in 

 cancer, are, in reality, somatic mitoses. Although we do not presume to 

 explain in the above manner all the figures which may be brought forward 

 resembling that form of nuclear division, we submit that the occurrence of 

 heterotypical mitoses in cancer requires further proof. Multipolar mitosis 

 and other irregular forms of cell-division occur in cancer, but they do not 

 supervene upon heterotypical mitosis. They are entirely independent of 

 its presence, and, of themselves, suffice to account for the diminutions 

 frecpuently occurring in the number of chromosomes in cancer throughout 

 the vertebrates. 



DESCRIPTION OF PLATES. 

 [Plates 5 and 6.] 



Fig. 1. — Apparent heterotypical mitosis. Transplanted cai-cinoma of mouse. Analysis of 

 ring, loop, and bivalent chromosomes (heterotypical). Replica of fig. 3 of Royal 

 Society paper, and of fig. 27, First Scientific Report, 1904. x 3000/1. 



Fig. 2. — Same section as fig. 1. Analysis after restaining, showing how a fortuitous 

 association of short somatic (longitudinally split) chromosomes gives the appearance 

 of bivalent elements. X 3000/1. 



Fig. 3. — Partial analysis of the remainder of the mitosis, of which part only is shown in 

 figs. 1 and 2. Longitudinally split chromosomes with limbs of unequal length lying 

 at various angles to the spindle axis. X 3000/1. 



Fig. 4.— Diagram of a somatic amphiaster. in which longitudinally split V-shaped 

 chromosomes, with limbs of unequal length, are apparently arranged parallel to the 

 spindle axis. Adjacent chromosomes, with their longer limbs on opposite sides of 

 the equator, if regarded as together forming one chromosome, would convert such a 

 mitosis into a heterotype with half the somatic number of chromosomes arranged 

 longitudinally on the spindle, e.g., figs. 3, 5, 6, 7, 8, 9, and 10. 



Figs. 5 and 6. — Apparent heterotypical mitosis. Fig. 5, replica of fig. 4, Royal Society 

 paper, and of fig. 26 in First Scientific Report, 1904. Transplanted carcinoma of 



* ' Centralb. f. Path. u. path. Anat.,' vol. 13, 1902. 

 t Loc. cit. 



