2 28 THE GERM -PLASM 



terable condition, or else of certain ids of the primary idioplasm 

 being added in an unalterable condition to the blastogenic 

 germ-plasm when it becomes separated from the primary idio- 

 plasm. 



As, apart from plants, gemmation only occurs in compara- 

 tively low forms of animals, viz., in the Coelenterata, Polyzoa, 

 and Tunicata, we may infer that the addition of this blastogenic 

 idioplasm, consisting of accurately graduated groups of deter- 

 minants, eventually reaches a limit, owing to the increasing 

 complexity of the structure of the animal and to the surprising 

 extent to which the number of determinants increases. 



According to our view, the cells of the Metazoa and Metaphyta 

 may not only be provided with the above-mentioned accessory 

 idioplasm, but may in addition contain primary ger7n-plas7n, and 

 these cells are to be found along the ' germ-tracks,^ — that is to 

 say, they are situated in the direct line of development which 

 leads from the ovum to the germ-cells which are eventually 

 formed from it. As each somatic cell is only controlled by one 

 of the large number of determinants belonging to the germ- 

 plasm, and as determinants cannot be produced spontaneously, 

 those cells which are to give rise to germ-cells must contain 

 unalterable germ-plasm in addition to the active determinants 

 which control them ; and the former can only be derived from 

 the cell to which the whole organism owes its origin, for this 

 alone contains the whole of the determinants organically united 

 to form germ-plasm. A series of cells containing germ-plasm 

 in the form of unalterable accessory idioplasm, must therefore be 

 traceable from the egg-cell to that region of the body which 

 sooner or later gives rise to germ-cells ; that is, there must be 

 a continuity of the germ-plasm. 



The number of germ-tracks in the lower plants and animals 

 is a very large one ; under normal circumstances, germ-cells are 

 not only found in very many parts, especially in the case of 

 animal- and plant-stocks, but new persons may in exceptional 

 cases be formed in many regions by budding, especially when 

 injuries to the stock have occurred ; and these persons can again 

 produce germ-cells. In the case of the Hydroid-polypes and 

 Polyzoa, a large number of cells of the stock must be provided 

 with germ-plasm, although it is impossible to say whether these 

 are the same as those which contain blastogenic idioplasm, or 

 whether the latter is situated in other adjacent cells which also 



