98 JOSE F. NONIDEZ 



Normal or degenerated, the granule-laden leucocytes and their 

 young stages may be preyed upon by special phagocytic cells 

 (figs. 19 to 21), which the writer would identify with the hemocy- 

 toblasts were it not for the fact that they show constant specific 

 differences. The phagocytic cells first appear in the hematopoi- 

 etic foci as elements no larger than dwarf hemocytoblasts, from 

 which they differ chiefly in the absence of a conspicuous sphere 

 and the nature of their cytoplasm, which is not basophilic and 

 shows a faint network (fig. 19). These cells grow until they 

 attain a considerable size, which may be still increased by the 

 presence of phagocytized cells in their cytoplasm. The homology 

 of the phagocytic cells with the histiotopic wandering cells is 

 also diflftcult to establish. According to Danchakoff ( '08 b) the 

 latter show a marked tendency toward polymorphism and are 

 endowed with phagocytic properties. They arise as a transfor- 

 mation in the undifferentiated mesenchyme cells and also as the 

 result of a peculiar evolution of the small lymphocytes. Since 

 the origin of the phagocytic cells present in the gonads could not 

 be traced, it seems advisable to speak of them as the 'phagocytic 

 cells' until further investigations show their true nature. Their 

 origin from the endothelial lining of the blood-vessels has been 

 suggested elsewhere (p. 91). 



Figures 20 and 21 represent two phagocytic cells which have 

 engulfed granulocytoblasts and granulocytes. The cell drawn in 

 figure 20 is binucleate. Phagocytosis of erythrocytes by hemo- 

 cytoblasts has been reported in the spleen by Danchakoff ('16 d, 

 fig. 19) and, although the figure given by this observer and figures 

 20 and 21 agree in many respects, yet the homology of both kinds 

 of cells is not backed by conclusive evidence on their common 

 origin. 



The phagocytic capacity of the endothelium was very con- 

 spicuous in sections of a piece of testis undergoing regeneration. 

 No granulocytes were present in this slide. Their place had 

 been taken by large numbers of small Ijonphocytes (fig. 22, 1) which 

 are produced in the mesenchyme as the result of a lymphoid 

 metaplasis, which will be described later. The small lympho- 

 .cjtes thus produced migrate toward the blood-vessels and even- 



