320 Papers from the Department of Marine Biology. 



Cell a is a typical primordial germ-celi. Ordinarily, in the inactive 

 condition, it has an oval form, rather than the more nearly spherical 

 form of the granulocyte in the same condition. Moreover, it is 

 nearly twice the size of the largest granulocyte. Its nucleus is vesicu- 

 lar, contains a very characteristic finely granular karyoplasm, and stains 

 only very lightly in basic dyes. The radial disposition of the rows of 

 oxyphiUc chromatin granules is striking. There is present usually 

 only one large, very chromatic, spherical or oval nucleus; and one (or 

 sometimes several) much smaller chromatic accessory nucleoU; and 

 usually one (sometimes several) pale plastin nucleoU. The cytoplasm 

 is more or less crowded with larger and smaller yolk spherules, staining 

 more or less deeply. It contains also abundant granular, bacillary, 

 beaded, and filiform mitochondria (fig. 2a, plate 1). 



The granules of the blood granulocyte, on the contrary, are quite 

 uniform in size and in their deep-staining quaUty. The nucleus of the 

 granulocyte also is relatively smaller, contains a relatively coarse 

 chromatic net-work, and stains much more deeply as a whole in basic 

 dyes. In anticipation of what follows it may here be stated to advan- 

 tage that primordial germ-cells of earher stages, including the 2-day 

 stage, are of approximately the size of those of the 11-day stage, only 

 occasionally shghtly smaller. The germ-cells are therefore always 

 larger than the largest granulocyte (plate 1, figs. 16 and 25), the largest 

 hemoblast (plate 1, fig. Ih), and the largest erythroblast (plate 1, 

 fig. 5). The nucleus of the germ-cell also is quite different from that 

 of any of the cells in close proximity to which it may be found — granu- 

 locyte (5), mesothelium (M), mesenchyma, hemoblast (h), erythro- 

 blast (fig. 5), and erythrocyte (plate 1, fig. le). It resembles closely 

 only the young entodermal cell, especially in respect of its nucleus, 

 from which cell the germ-cell can, however, be distinguished by criteria 

 which will be given below. Moreover, the granulocyte may assume 

 most varied shapes, at different stages of amoeboid progression; the 

 germ-cell, while also capable of amoeboid movement, becomes less 

 irregularly modified, extreme forms being represented in figure 3, 

 aa, ah, ac, plate 1. 



In the Helly fixed tissue, stained with Giemsa, the granules of the 

 blood granulocytes stain either blue or red, depending upon the 

 phase of development of the cells. The majority of the cells at this 

 stage contain red-staining granules; a few contain only unripe blue- 

 staining granules; and a certain number have mixed granules, including 

 all phases of the ripening process of an eosinophil granule. The 

 nucleus also stains a deep blue. The primordial germ-cell of this 

 tissue, on the contrary, has a fight bluish-pink-staining nucleus, with 

 a deep purple nucleolus. The cytoplasm of the germ-cell is vacuolated, 

 the vacuoles being the negative of the dissolved yolk-globules; and it 

 has a coarsely reticular character in consequence, and stains only 

 faintly pink. 



