48 



Si)mewliat «!iaj*rammati(; sections of an embryo of mjii luifis, 2'H6 m.m. in lenj*th. 

 a. l-'ij;. A is a j;criTi-L-ell near the site of the future strminal nidus : c, lyinj; between the 

 epiblast and hypoblast is in migration 



a. Fig. B, is a germ-cell lying within the mesoblast. 



The blastoderm is seen crowded with germ-cells (After .Inhn Beard). 



This embryo contained but two germ-cells within the 

 " embryonic foundation," one of these shown at a, Fi^;. A 

 occupies the site of the future " germinal nidus." The upper 

 part of the blastoderm just outside the embryo is crowded with 

 aerm-cells. From this crowd germ-cell a. has evidently 

 migrated, while germ-cell c. has evidently commenced 

 migration. Further, at the close of the segmentation, before 

 there is any embryo at all, the germ-cells are represented by 

 cells 0*02 m.m., or 0"036 m.m. diameter. Normal germ-cells 

 have a diameter of 0-02 m.m. 



To give emphasis to the fact that germ-cells cannot 

 possibly be the products of the embryo. Beard maUes the 

 following statement with regard to embryos 2 or 3 m.m. in 

 length. " hi the growing zone of the developing embryo there 

 " are no cells at any time large enough to he the progenitors of 

 " the germ-cells." * 



The presence of misplaced germ-cells in the embryo has 

 long been known. Little note, however, has been taken of the 

 knowledge. The cells referred to by Beard as germ-cells in 

 pre-embryonic and early embryonic development have also 

 long been known. They have not, however, been recognised 

 as such, but have been regarded as pertaining to other 

 structures. Beard, however, in his published papers deals satis- 

 factorily with these. For instance, Riickert in his work on 

 Torpedo embryos, makes reference to certain large yolk-laden 



• John Beard. "The Germ-cells. Part I," Journal nf Aiuitnmy ami Physiology. 

 Jan., 1904, p. 218. 



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