June. 1921,] KUWADA:- LONGITUDINAL SPLIT OF CHROMOSOMES 103 



the morphology and gen cji of old and new chromosomes seem quite 

 to coincide in the plant and the animal. 



The anastomoses between, as well as inside the old chromosomes 

 gradually disappear, and the new chromosomes, occupying the place 

 of the old ones, and retaining their zigzag or coiled form, run dis- 

 tinctly free from their neighbours. Fig. 8 represents a nucleus in this 

 stage. This may , however, be a little abnormal, in the possession of 

 a little more of the chromatic substances, though it is not a rare 

 occurrence. These chromosomes run mostly parallel with each other, 

 and also, not infrequently, show a tendency to converge towards the 

 nucleolus especially in round nuclei. Fig. 7, which presents an earlier 

 stage than that of Fig. 8, shows ver}^ well one of the situations, 

 although the material is not well fixed, being treated with the fixa- 

 tive for 12 hours, so that the figure presents a somewhat abnormal 

 appearance from the fact that much more chromatic substances are 

 found in the old chromosomes than in those well fixed, and the new 

 chromosomes are too obscure to show their morphological details. 

 The new coiled chromosomes begin to get loose, to straighten out, 

 and to equalize. When this stage is reached, the longitudinal split 

 of chromosomes appears to be seen for the first time in places (Fig. 

 9). The straighter and more equalized the chromosomes become, the 

 more distinctly the split appears (Fig. 10). Up to these stages no 

 sign of split has been seen with accuracy. In the stage represented 

 by Fig. 8 whether the split begins to appear or not remains un- 

 determined. 



As will be seen by the foregoing, it seems probable that the ar- 

 rangement of the essential parts of chromosomes is in a form ap- 

 proaching a zigzag or coil through the telophase and resting stage 

 up to the formation of the new chromosomes in the next prophase. 

 A light line in the axis of anaphasic chromosomes, which is interpre- 

 ted by some authors to be an axial vacuolization of chromosomes or 

 a phenomenon due to the different consistency in the axial and peri- 

 pheral portion, may be interesting in connection with the feature of 

 chromosomes in the telophase. The coiled, new chromosomes become 

 straightened out, become longitudinally split and shorten again into 

 •the thicker and shorter definitive chromosomes, getting more chroma- 

 tic substances during the processes. We have no adequate evidence, 

 at present, to solve the question as to how the essential parts of 

 chromosomes are arranged in the condensed chromosomes ; but there 



