THE GONADS OF THE FOWL 87 



The study of sections of the testis in chick embryos after the 

 ninth day of incubation shows the occurrence of hematopoietic 

 foci in the mesenchyme lying between the sexual cords and young 

 seminal tubules (fig. 7). As stated above, the most conspicuous 

 elements in these hematopoietic foci are the cells possessing gran- 

 ules in their cytoplasm, which stain red after treatment with 

 eosin and deep black in the iron-hematoxylin slides. The size of 

 the granules is variable, even within the same cell (fig. 14). 

 While the morphological characteristics of the cytoplasm and 

 its contents seem to be uniform in these cells, the structure of 

 their nuclei varies a good deal. In this respect, the granule- 

 laden cells both in the testis and ovary fall into two groups: in 

 one may be placed all the cells in which the nucleus is round or 

 oval in outline (myeloblasts, granulocytoblasts, figs. 11 to 14), 

 while in the other the nucleus is polymorphic and often broken 

 into two or three portions (granular leucocytes, granulocytes, figs. 

 7, 15, and 18, g). These two kinds of cells are the extremes of a 

 closely graded series, whose stages, which overlap each other in 

 perfect sequence, may be found lying side by side in the same 

 hematopoietic agglomeration (figs. 7, 15, and 18). 



In addition to these elements cells may be found in which no 

 granules occur in the cytoplasm, which is strongly basophile. 

 The nucleus of these cells is round or oval in outline (fig. 2, h' , 

 and figs. 15 and 18), but in the young cells may show a marked 

 tendency toward polymorphism; it contains a faint chromatin 

 network and one or two large karyosomes, which stain a deep 

 black after the iron hematoxylin, but show their compound 

 nature in slides stained with Delafield hematoxylin and eosin. 

 The elements just described obviously correspond to the large 

 lymphocytes or hemocytoblasts (Danchakoff, '16 d)^ which 

 according to the observers of the monophyletic school are the 

 common stem-cells for all the elements of the blood. The extra- 



' In order to avoid the use of synonyms, the nomenclature suggested by Dan- 

 chakoff ('16, d, p. 272) will be used throughout the following pages. In this 

 nomenclature the old term 'large lymphocyte' has been substituted by lymphoid 

 hemocytoblast. Granulocytoblast and granulocyte are equivalent to myeloblast 

 and granular leucocyte (myelocyte), respectively. 



