200 THE GERM-PI^SxM 



to its parent depends. The theory of the continuity of the germ- 

 plasm, as I understand it, is not based on the fact that each 

 ' gemmule ' necessary for the construction of the soma is present 

 many times over, so that a residue remains from which the germ- 

 cells of the next generation may be formed : it is founded on the 

 view of the existence of a special adaptation, which is inevitable 

 in the case of multicellular organisms, and which consists in the 

 germ-plasm of the fertilised egg-cell becoming doubled primarily, 

 one of the resulting portions being reserved for the formation of 

 germ-cells. 



Gustav Jager * was the first to express the idea that in the 

 higher organisms the body consists of two kinds of cells, which 

 he calls respectively ' ontogentic ' and ' phylogentic ; ' and that 

 the latter, or reproductive cells, are not a product of the former, 

 or body-cells, but are derived directly from the germ-cell of the 

 parent. f He took it for granted that the '■ formation of repro- 

 ductive substances occurs in an animal during the early em- 

 bryonic stages,' and imagined that he had thus proved the 

 existence of a connection between the germ-cells of the parent 

 and those of the child. Although these opinions were not 

 founded on fact or followed out in detail, they ought to have led 

 to further ideas on the subject. They, however, together with 

 the book in which they were contained, remained unnoticed. 



A few casual remarks made by Rauber,:}: in a paper on ' Form- 

 bildung und Formstorung in der Entwicklung von Wirbelthieren,' 



* Gustav jager, ' Lehrbuch der allgemeinen Zoologie,' Leipzig, 1878, 

 II. Abtheilung. 



t The praiseworthy attempt to do justice to my predecessors in this par- 

 ticular subject has perhaps been carried too far. In Geddes and Thomson's 

 ' Evolution of Sex' (p. 93), for instance, a quotation is given from Jager 

 which seems to prove that he anticipated me with regard to the theory 

 under consideration. The quotation in which this idea is expressed is, 

 however, not taken from the book published in 1878, but from an essay 

 written ten years later, and it concludes with the following words: — 'This 

 reservation of the phylogenetic material l\lescribed as t/ie continuity of the 

 germ-plasm' But no mention is made by Jager of the continuity of the 

 germ-plasm in his book v/hich appeared in 1878, in which a connection 

 between the germ-t^//j of different generations is supposed to exist: — and 

 this is not the case. The entirely new statement of his ideas has been 

 influenced by those contained in my essays which had appeared in the 

 meanwhile. 



+ ' Morphol. Jahrbuch,' Bd. 6, 1880. 



