96 RHODA ERDMANN 



This comparison could be continued but the facts prove already 

 that among connective tissue cells of the most varied parts of 

 the chicken body these elongated, finely vacuolized, slender cells 

 appear with a true connective tissue cell nucleus. They are all 

 similar to the figures of Foot representing his X cells (cf. Foot 

 '12, plate 22, figures 8, 16, 19). The connective tissue cell rep- 

 resented by the present writer in figure 9, is taken from a young 

 chicken and is not of the same size as some of those cells which 

 Foot shows. When cells, however, were taken from the bone 

 marrow of a full-grown chicken, they were of the same dimen- 

 sions as those given by Foot, '12, plate 22, figure 8. 



Also, in the development of embryonic bone marrow tissue of 

 the chicken, Dantschakoff, '09, depicts mesenchyme cells (plate 44, 

 figures 5 and 6) which have a close resemblance to the above men- 

 tioned cell type (fig. 9). They are identical types, except that 

 the latter may contain fat, the first are fatless. In this group 

 must also be included the elongated forms of Foot's Riesenzellen 

 which have pointed pseudopods. 



To summarize: Though fat containing and often vacuolized 

 the elongated cells with connection tissue like nuclear structure 

 which appear in Foot's figures among his 'Riesenzellen' are true 

 connective tissue cells. There can be no doubt that the granular 

 lymphocytes, the elongated cells of connective tissue charac- 

 ter, and the endothelial cells did not originate de novo in the tis- 

 sue culture. 



In studying the cells close to the connective tissue network of 

 the bone marrow the present wTiter could only distinguish one 

 well defined cell type (figs. 36 and 37). Small round cells with 

 strongly basophil cytoplasm and large, faintly staining nucleus 

 with two nucleoli are abundant. They are neither microlym- 

 phocytes nor mononuclear lymphocytes nor erythroblasts. They 

 differ from the microlymphocytes by their vesicular nuclei, from 

 the mononuclear lymphocytes by their size and their cytoplasm, 

 from the erythroblasts by their nearly chromatinless nuclei and 

 also by their size. In living cells the nuclei of erythroblasts ap- 

 pear whitish, the nuclei of these cells dark. If these cells, 

 which migrate from the tissue particle after the leucocytes are 



