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THE AMERICAN NATURALIST 



[Vol. XLVII 



On the other hand, to Nussbaum is sometimes credited the 

 theory of germinal continuity, but in such cases authors appar- 

 ently do not sharply distinguish continuity of the germ-plasm 

 from continuity of the germ-cells. Thus Minot 17 says : 



We owe to Moritz Nussbaum the theory of germinal continuity— the 

 only theory of heredity which seems tenable at the present time. 

 According to this theory, the germ-cells are set aside during the seg- 

 mentation of the ovum and preserve the essentially undifferentiated 



of which they arise. 



However, irrespective of the conclusions that may be reached 

 as to whom priority in the statement of the theory of germinal 

 continuity belongs, it is to Weismann that credit must be given 

 for the development of this doctrine into an important theory 

 of heredity. 



There would seem to be a gain in precision and clearness of 

 expression in discussions involving the idea of continuity in 

 development if a distinction were always made between (1) 

 genetic continuity, or biogenesis, (2) genetic cellular contin- 

 uity, (3) continuity of the germ-cell and (4) germinal con- 

 tinuity. Thus restricted the term germinal continuity expresses 

 more closely the conception held by the greatest exponent of this 

 theory. Since Jiiger first used the phrase "Continuity of the 

 Germ-plasm" I suggest that his name be linked with that of 

 Weismann in referring to this principle, which may well be 

 called the Jager-Weismann Law of Germinal Continuity, the 

 esential doctrine of which is thus expressed: 18 



In each ontogeny, a part of the specific germ-plasm contained in the 

 parent egg-cell is not used up in the construction of the body of the 

 offspring, hut is reserved unchanged for the formation of the germ- 

 cells of the following generation. 



However, the real significance of Weismann 's theory of ger- 

 minal continuity and its bearing on theories of heredity can not 

 be fully appreciated without at least a general acquaintance 

 with the somewhat voluminous literature of this subject. 



an, A., "Essays upon Heredity and Kindred Biological Prob- 

 rized translation, 2d edition, Oxford, 1891, p. 170. 



