370 ELIOT R. CLARK 



H 2 , X 1 and A T . A few cells such as cell D, (D l and D 2 ) moved 

 from the interior toward the surface. One cell, R, which for a 

 time was spread out in part under one epidermal layer, and in 

 part under the other, gradually withdrew one set of processes 

 until it was eventually entirely on one side. 



In addition to the amoeboid wandering, another striking change 

 takes place in these cells, namely, mitotic division. This process 

 has been figured and briefly described by Haidenhain. 5 My 

 findings agree in the main, with his, the chief difference being 

 that, while he states that the cells after division become fixed, 

 I find that, while movements are most rapid at the time of divi- 

 sion, yet after, as well as before, the cells are not 'fixed' but are 

 distinctly motile. The changes which take place during the divi- 

 sion of the cell are as follows (fig. 14). The thick central 

 portion of the cell swells and the processes become shorter and 

 thicker at the base and some are entirely withdrawn (fig. 14, 

 A and B). The spireme appears as dark spots which soon form 

 in a line across the equator of the cell (fig. 14, C), this line divides 

 rapidly and the chromosomes as two sets of lines move in opposite 

 directions to the poles, where they shorten and become moulded 

 into spheres, the two daughter nuclei. These nuclei are clearly 

 visible for only a short time. The moving apart of the chromo- 

 somes takes place rapidly — so rapidly in fact that the movement 

 may be seen. Four minutes after their arrangement in the equa- 

 torial plane, they are well separated, and form the typical group- 

 ings at the poles. Five minutes later the rounded nuclei are 

 formed and fifteen minutes later the nuclear outlines are lost 

 and the nuclei can no longer be distinguished in the living cell. 

 The remainder of the cell with all of its processes shortened and 

 some entirely withdrawn has a clear, glassy appearance during 

 division. The concentration of the protoplasm in the neighbor- 

 hood of the nucleus is most marked at the time when the chromo- 

 somes are moving apart. As soon as the chromosomes are well 

 separated, the cutting in of the protoplasm commences. The 

 pear-shaped body of the cell lengthens to a cylindrical shape, 



5 Haidenhain, Plasma und zelle 2e. Lief. pp. 721 and 722 in Bardelebens Hand- 

 buch der Anatomie des Menschen, Jena, 1911. 



