80 ' DETEEMINANTS ' VERSUS 



ductive cells ' ; that there is a strict continuity of the latter from 

 one generation to another, and that they never take origin afresh, 

 in the course of an individual's development, as liver cells, kidney 

 cells, or brain cells are known to do. 



But what are the facts ? It is a matter of common knowledge, 

 and admitted by Weismann himself, that the fertilised ovum 

 segments into hundreds, "thousands or even millions of cells" 

 before, in some animals, the primary germ-cell appears in the 

 rudiments of the ovary.' And speaking of this latter he says in 

 his last work ("The Evolution Theory," I, p. 300) :— " We find 

 that it consists of a single primitive egg-cell, from which, by 

 division, all the other egg-cells arise. In the same way the first 

 rudiment in the testis or spermary is formed by a primitive sperm- 

 cell which does not differ visibly from the primitive egg-cell. Both 

 now multiply by division for a considerable time." Where then, 

 it may be asked, is the alleged continuity of the germ-plasm ? 

 Only another " assumption " is needed to bring this about. Thus 

 further on (p. 410) he says the ' primordial germ-cell ' makes its 

 appearance, " usually during embryogenesis, and often very early 

 in it, after the first few divisions of the ovum, but sometimes not 

 till long after the end of embryogenesis ; and not even in the 

 individual which arises from the ovum, but in descendants which 

 arise from it by budding. Here the primordial germ-cell is sepa- 

 rated from the ovum by a long series of cell-generations, and the 

 sole possibihty of explaining the presence of germ-plasm in this 

 primordial cell is to be found in the assumption = that in the divisions 

 of the ovum the whole of the germ-plasm originally contained in 

 it was not broken up into determinant groups, but that a part, 

 perhaps the greater part, was handed on in a latent state from cell 

 to cell, till sooner or later it reached a cell which it stamped [why 

 that rather than any previous cell ?] as the primordial germ-cell. 

 Theoretically it makes no difference whether these ' germ-tracks,' 

 that is, the cell-generations which lead from the ovum to the 

 primordial germ-cell, are short or very long, whether they consist of 

 three or six or sixteen cells, or of hundreds and thousands of cells." 

 As to the reality of the existence of such ' germ-tracks ' not a tittle 

 of evidence is given, or even attempted. Weismann's ever-ready 

 assumptions cannot be accepted as proofs — so that many of us can 

 only regard his doctrine of the " continuity of the germ-plasm " 



■ "The Germ Plasm," 1893, p. 193. ' No italics in original, 



