PLATE 6 



EXPLANATION OF FIGURES 



12 and 13 Differentiation of small lymphocytes in the follicle anlages. Fig- 

 ure 12 shows the center of a follicle, figure 13 a part of a follicle adjacent to the 

 pulpa. M.Rtc, mesenchymal reticulum; Sl.L.Hbl., group of lymphoid hemo- 

 cytoblasts forming a kind of syncytium; Y, amitotic division of a nucleus in a 

 reticulum cell; X, intermediate stage between a lymphoid hemocytoblast and a 

 small l>Tiiphocyte. Fifteenth day of incubation. 



14 Different stages of amitotical division of the nucleus; a, b, c, in mesenchy- 

 mal cells, d in a free cell. 



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