On the Occurrence of Heterotypical Mitoses in Cancer. 227 



also illustrated some of the appearances simulating bivalent chromosomes, 

 but in reality conforming to the type met with in ordinary (somatic) 

 karyokinetic cell-division.* In what follows we shall illustrate other sources 

 of error on the basis of a renewed analysis of the preparations from which 

 the figures of heterotypical mitosis in our previous papers were made and by 

 other figures not yet published. 



In the sexual cells of animals the heterotypical mitosis is preceded by a 

 stage known as the " synapsis." In it the chromatin filament is split 

 longitudinally and gathered into a rosette at one part of the nucleus, the 

 nucleolus lying to one side and usually flattened against the nuclear 

 membrane. In this stage the chromosomes are believed to unite in pairs., 

 thus giving rise in the equatorial plate of the heterotypical mitosis to 

 bivalent chromosomes, half as numerous as those characteristic of ordinary 

 somatic cells. The examination of many sporadic and transplanted 

 malignant new growths failed to reveal a corresponding sequence in their 

 nuclei. We therefore undertook a renewed analysis of the preparations of 

 the stages in cell-division already figured from transplanted mouse tumours, 

 and of other preparations resembling them, to determine whether or not 

 their identification as heterotypical were justified. We shall confine our 

 statements mainly to five transplantable mouse tumours because they permit 

 of control observations with varying methods of preservation and staining in 

 a manner not possible with material from sporadic new growths ; but our 

 remarks apply also to the figures we have published from sporadic tumours of 

 the trout and cat. 



Von Hansemannf has combated the statements on the presence of hetero- 

 typical mitoses in malignant growths, and ascribes the appearances figured to 

 clumping of the chromosomes, and to pathological abnormalities in their 

 form. He adheres to his conclusion that the numerical diminution is not an 

 exact halving of the normal number, but is irregular, and due to (1) asym- 

 metrical mitosis, and (2) casting out and degeneration of chromosomes. 

 Hacker reproduced three of our figures in a paper in which he admitted the 

 striking similarity to heterotypical mitosis, but suggested that adhesion of 

 the chromosomes in pairs,}: together with longitudinal splitting of the couples 



* Loc. cit. 



t ' Biolog. Centralb.,' vol. 24, 1904 ; vol. 25, 1905 ; ' Verhandl. physiol. Ges.,' Berlin, 

 1904. 



% Hacker uses the term " heterotypical " in a purely morphological sense, and embraces 

 in it the mitoses of the cells destined to give rise to the sexual products of Ascaris and the 

 Copepods, In the latter he has shown that exposure to ether ('Anat. Anzeiger,' 1900) 

 may cause all the cells of the developing egg to exhibit this modification (viz., cohesion 

 of the chromosomes in pairs). In the strict sense of the word, the term " heterotype ,; is 



