. The Biological bulletin. Biology; Zoology; Marine biology. NUCLEAR CHANGES IN RANA CLAMITANS. 131 by amoeboid movement of the cells. Figure 9 shows a section through one side of the cord, in which one layer of cells, not quite at the end, is extending down into the central canal. Up to about six days phenomena such as these may be seen, but sections from six to sixteen days show that the closing is not completed within that period. By sixteen days the new tail is. Fig. II. Sagittal section through the spinal cord one day after the operation showing the granular leucocytes at the end of the c
. The Biological bulletin. Biology; Zoology; Marine biology. NUCLEAR CHANGES IN RANA CLAMITANS. 131 by amoeboid movement of the cells. Figure 9 shows a section through one side of the cord, in which one layer of cells, not quite at the end, is extending down into the central canal. Up to about six days phenomena such as these may be seen, but sections from six to sixteen days show that the closing is not completed within that period. By sixteen days the new tail is. Fig. II. Sagittal section through the spinal cord one day after the operation showing the granular leucocytes at the end of the cord, and the pulling apart of nuclei in the lower part of the cord, cc, central canal; Ic, leucocytes. (920 di- ameters.) almost as long as it will become (Durbin, 1909), and the spinal cord reaches back close to the epidermis at the posterior end. Still these later preparations show the sides of the neural tube gaping open, and red blood corpuscles extending forward into the central canal of the new cord, as if the pressure of the cerebro- spinal fluid is not sufficient to keep them out. 4. Cell Division. In an organ such as the spinal cord in which the nuclei lie close together, it is difficult to determine an amitotic division. In order to be sure that amitotic divisions do occur, one must find continuous stages in nuclear and cellular constriction without the formation of chromosomes. Because of the massing of nuclei, this cannot readily be determined in the normal spinal cord, though the slides were examined with this point in mind. The present study gives no evidence that normal nuclei divide amitotically, but stages in direct division can be seen in the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-; Marin
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