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Nachdruck verboten. 



The Numerical Law of the Grerm-Cells. 



By J. Beabd, D. Sc, 

 University Lecturer in Comparative Embryology, Edinburgh. 



Given a set of germ -cells and an embryo, a priori there are 

 broadly two possible alternatives as to their relationships. These are 

 1) that the embryo may have formed the germ-cells, and 2) that the 

 germ-cells were first upon the scene, and, as a consequence, that the 

 ''parentage" of the embryo may be referred to one or more of them. 

 In some form or other the former of these views underlies practically 

 all current embryological teaching, just as it sways our social ideas 

 as to parentage, etc. So difficult was it to escape from the conclusion 

 as to a genetic connection between the embryo and the germ - cells 

 contained within it, of such a kind that the latter were to be regarded 

 as the "offspring" of the former, that the hypothesis of a special germ- 

 plasm, continuous from generation to generation, was set up. 



With the repudiation of a somatic origin of germ-cells, on the one 

 hand, and of the necessary existence of a hypothetical intangible germ- 

 plasm, on the other, to what must a resort be made in explanation 

 of germinal continuity? As elsewhere^) briefly outlined for the skate, 

 Raja batis, the track of heredity in Weismann's sense from generation 



1) J. Beard, The Morphological Continuity of the Germ -Cells in 

 Raja batis. Anat. Anz., Bd. 18, 1900, p. 484—485. 



