496 Mr. C. E. Walker. [May 15, 



seemed to be mutual on the part of two contiguous leucocytes (fig. 1). These 

 protrusions were quite different in character from the processes which are 

 sent out by the nuclei in polymorphonuclear leucocytes and myeloplaxes, 

 and from the appearances presented during the phenomenon of amitosis. 



Shortly after the nuclear protrusions had reached the periphery of the 

 cytoplasm, which was always reached at adjacent points of the contiguous 

 cells, the ends of the protrusions joined.* After the joining of these two 

 processes, a ring of chromatin masses appeared at either end, a short distance 

 outside the points where the peripheries of the respective nuclei of the two 

 cells would have been if no protrusions had been formed (fig. 2). Strands 

 of chromatin extended from these masses just under the membrane of both 

 nuclei, and also along the tube which joined them. Other strands seemed to 

 pass along the tube between the two nuclei. After this apparatus had been 

 fully formed, the chromatin in one of the two nuclei began to disappear, and 

 the amount of chromatin in the other was frequently very markedly increased. 

 This process continued until one nucleus was completely denuded of its 

 chromatin, and the nuclear membrane collapsed (figs. 2 and 3). The 

 chromatin ring at the end of the tube contiguous to the collapsing nucleus 

 remained long after the other had disappeared, and sometimes the termination 

 of the tube and the ring appeared in a shape something like an acorn on a 

 stalk (fig. 3). While this process seemed to be quite constant in so far as 

 the disappearance of the chromatin from one of the nuclei was concerned, the 

 increase of the chromatin contained in the other nucleus was not always very 

 apparent. Frequently, however, there was no doubt that a very large increase 

 indeed had occurred. 



The leucocytes of Axolotl upon which these observations were made were, 

 of course, in a more or less abnormal condition, but in view of the relatively 

 small size of mammalian cells when compared with those of Axolotl,f it 

 appeared likely that what was very striking in the case of the large cell 

 might easily be missed in the case of the small. Some slides of normal 

 mammalian tissues (bone-marrow, spleen, lymphatic gland, etc.) were 

 re-examined, and all the stages in the phenomenon described above, excepting 



* It can but rarely happen that two contiguous cells will be in such a position in the 

 section that the mutual sending out of nuclear processes will be presented to the observer 

 in profile, as shown in fig. 1. Much more often either only one of the two cells will be 

 found in the same section, or the two will be super-imposed either directly or at an angle. 

 The phenomenon is therefore probably more common than would at first sight appear, as 

 anything but a lateral presentation of the two cells would be difficult, often impossible, 

 to interpret. 



t Compare figs. 1 — 3 with figs. 4 — 9, which give a fairly accurate idea of the relative 

 sizes of these cells. 



