124. Victor E. Emmel. 
have not succeeded even in determining whether the stimulus thus 
controlling the cell activity is some “chemical peculiarity” of the 
injured and exposed tissue, or whether it is some “‘inter-action” of 
the epidermal cells, questions which are merely preliminary to under- 
standing the factors which may account for the apparent polarization 
of nuclear contents just described. These nuclear changes might 
possibly be classed among the phenomena designated as ‘“‘cytotaxis” 
(Roux, 796), although in doing so it is not evident that we advance 
materially in a solution of the problem. At the end of the next 
fourteen hours, 7. e., thirty-eight hours after autotomy, the epidermal 
cells have spread completely over the stump and the first mitotic cell 
division appears. During this period the nuclei have assumed a 
more spherical form and appear somewhat larger. Both the nuclear 
sap and chromatin have become more equally distributed. The 
chromatin is now more coarsely granular, and as the nucleus ap- 
proaches the prophase of mitosis, the chromatin collects in con- 
spicuous rod and knot-like masses or chromosomes (Fig. 14, a). The 
nuclear membrane then disappears and the cell passes through the vari- 
ous mitotic phases, of which a later metaphase is shown in Fig. 14, D. 
The volumetric increase of nuclear material during the initial regen- 
erative activities presents another fact for consideration. In many 
respects the problem arising from the phenomena of cytomorphosis 
and regulation in the reproduction of a part of the organism are 
comparable with similar problems in the development of the original 
embryo. In both processes the differentiation of anatomical structure 
is preceded by the formation of a more or less undifferentiated mass 
of cells, characterized, in the case of embryonic development, by 
the segmentation of the ovum, and in the case of regeneration, by 
the proliferation of a mass of cells from the tissues in the region 
of injury. While the present data hardly justify an extended dis- 
cussion, attention may, however, be called to the fact that in both 
regenerative and ontogenetic processes, the initial cytological changes 
are attended by a characteristic increase in the amount of nuclear 
material.‘ 
‘It should be observed that in the case of regeneration, at least in the earlier 
stages, the increase of nuclear material apparently is not associated with cell 
division. 
