Difference Between Somatic and Germ-Tracks 103 



them for the fulfillment of the functions still devolving 

 upon it. 



Therefore, we have here an instance of a somatic path 

 without latent hereditary qualities. At least, this is as 

 certain as observation can make it in the present state of 

 our knowledge. And it is evident that this instance com- 

 pels the assumption that on many other somatic tracks, as 

 well, a reduction of the hereditary characters, although 

 less extensive, may take place. But since our task is to 

 group facts, and not to make assumptions, we shall not 

 discuss this point any further. 



8. The Difference Between Somatic Tracks and Germ- 

 Tracks 



We see now before us the rough lines of the picture 

 of the cell-pedigrees for the higher plants. And whoever 

 followed my description attentively, will have seen that 

 the picture is a purely empirical one, in which the promi- 

 nent lines are indeed arbitrarily chosen, but have been 

 drawn without any hypothesis. Especially is the differ- 

 ence between the somatic and the germ-tracks purely a 

 matter of fact, and in harmony with our present knowl- 

 edge. It claims nothing except to serve as an indication as 

 to whether any cell can, through its descendents, con- 

 tribute to the propagation of the species. 



But, as a basis for theoretical considerations, the cell- 

 pedigrees will attain their full value only when we have 

 realized the significance of the difference between somatic 

 and germ-tracks. This is by no means a difference in 

 kind, but one of degree. 19 This becomes clearest to us 

 when we try to define the limit exactly. We shall find, 



19 Weismann, A. Zur Annahme einer Kontinuitat des Keim- 

 plasmas. Ber. Naturf. Ges. Freiburg. 1: 7. 1886. 



