228 Dr. E. F. Bashford and Mr. J. A. Murray. [Nov. 2, 



thus produced, might account for the phenomena encountered in cancer. 

 The appearances in some preparations are explicable in the manner suggested 

 by von Hansemann,* but all the forms of cell-division resembling the hetero- 

 typical mitoses of reproductive tissue cannot be accounted for in this 

 manner. 



Some of the nuclear divisions previously figured have been found on 

 re-examination to be due to an artificial grouping together of distinct 

 chromosomes, fig. 1, reproducing at higher magnification fig. 3 of our 

 Royal Society paper, and fig. 27 of the First Scientific Eeport of the 

 Imperial Cancer Eesearch Fund, affords an example of this source of 

 confusion. The chromosomes seem to be bivalent, i.e., to have the form of 

 rings and loops. This mitosis is not completely depicted in fig. 1, the 

 remainder of the chromosomes being in the next section. The preparation 

 has been carefully restained. The result is shown in figs. 2 and 3. The 

 " rings " and " loops " resolve themselves into a larger number of ordinary 

 short chromosomes, split longitudinally. The dense equatorial plate of the 

 next section shows clearly the presence of many short chromosomes split 

 longitudinally, and arranged in the manner described below. The mitosis is 

 therefore somatic, and not heterotypical. 



The ordinary scheme of karyokinetic cell-division presents, in its phase of 

 equilibrium (amphiaster or equatorial plate), a series of Y-shaped loops with 

 limbs of equal length, arranged around a central spindle and all lying in a 

 plane at right angles to its axis. This arrangement is by no means universal. 

 Some of the deviations are of great importance to a proper understanding of 

 what occurs in cancer. Frequently the limbs of the V-shaped loops are of 

 unequal length. When this is the case the attraction fibres are relatively 

 few in number and attached only to the apex of the V and its immediate 

 vicinity, and therefore nearer one end of each chromosome than the other. 



applied to the form of mitosis charactet istic of the first ripening division of the spermato- 

 cytes of amphibia, as first described by Fleming. In the Salamander, ring-shaped chromo- 

 somes, half as numerous as the longitudinally split chromosomes of somatic mitoses, are 

 stretched out into elongated ellipses upon the spindle, giving rise to a barrel-shaped 

 figure. Chromosomes of similar form are associated with their numerical reduction in 

 many animals and plants, but it must be borne in mind that different forms of chromo- 

 somes occur in the corresponding mitoses of some animals. In Ascaris, e.g., both ripening 

 divisions appear to be effected by a longitudinal splitting of chromosomes arranged 

 transversely on the spindle, and in others ring or loop chromosomes are never formed. 

 It was, of course, conceivable that reduction-divisions might occur in cancer by means of 

 chromosomes unlike those in the reproductive tissues of the same animal. The frequency 

 of cells with diminished numbers of chromosomes led us to examine many tumours for 

 evidence of their occurrence, but without result. 

 * ' Biolog. Centralb.,' vol. 24, 1904. 



