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



studied and described in detail by Th.* and M.f Boveri in invertebrates : figs. 13, 

 14, and 15, from a squamous cell carcinoma of the tongue (human), represent 

 a cell in this condition. The nuclear membrane has disappeared, but there is 

 no trace of radiations or centrosomes to be seen. The chromosomes are 

 arranged as a hollow sphere around a central clear area, and for the most 

 part consist of two parallel daughter elements in different stages of separa- 

 tion. Some chromosomes in which the separation of the daughter elements 

 is least advanced have a horse-shoe shape. In others, the daughter elements 

 are parallel and widely separated. In a few, the separation is incomplete, 

 the ends only remain apposed, giving the appearance of rings. In fig. 13 

 this cell has a striking resemblance to a heterotypical mitosis such as occurs 

 in testis. Its cytoplasm is clear and voluminous, and there are no inter- 

 cellular bridges between it and the surrounding epithelial cells. The number 

 of chromosomes in the cell, however, is not diminished, but amounts to 

 45 to 50 when both sections are examined. Such a mitosis, instead of 

 reducing the number to half, really results in the original number of chromo- 

 somes being doubled, because the separated halves of the chromosomes 

 combine again to form a single nucleus. 



After elimination of these sources of confusion, there remain other 

 apparent heterotypical mitoses which cannot be explained in any of these 

 ways. The chromosomes present an irregular contour and become drawn 

 out like a viscid fluid in the later stages of separation. Individual chromo- 

 somes cannot be made out. The achromatic spindle develops at such a rate 

 that the evolution of the chromosomes cannot keep pace with it, and they 

 are drawn towards the spindle and stretched upon it before they have 

 completely contracted and condensed. 



All these abnormalities may occur in nuclei possessing the usual number 

 of chromosomes. They also occur in cells with a greater or lesser number 

 associated with the presence of multipolar and asymmetrical mitoses in 

 other cells. In such cases there is no evidence warranting the assumption 

 that the diminution in the number of the chromosomes is due solely to a 

 nuclear division effecting a reduction comparable to that of the sexual cells. 



Galleottit and von Hansemann§ have shown that nuclei with diminished 

 numbers of chromosomes (hypo-chromatic) may arise from larger ones by 

 asymmetrical mitosis, in which entire chromosomes pass to one daughter 



* Th. Boveri, ' Sitz.-ber. Phys.-med. Ges.,' Wiirzburg, 1897 ; ' Zellenstudien,' vol. 4, 

 Jena, 1901. 



t M. Boveri, 'Jen. Zeitschr. f. Naturwiss,' vol. 37, 1903. 

 | 'Ziegler's Beitr.,' vol. 14, 1893. 

 § Loc. vit. 



