BODY AND GERM-CELLS 



23 



give rise to egg-cells or sperm-cells rather than to muscle, 

 bone, or any other part of the body proper. Weismann called 

 the cells which collectively make up the body the soma (Greek 

 for body) ; whereas those undifferentiated cells destined for 

 reproduction he called germ-cells or collectively the germ- 



Fig. 8. Fruits of an apple " graft-hybrid " or " chimera." Two distinct varieties are represented in 

 one fruit. The stem-end of the apple is russet and sour; the blossom-end is smooth-skinned, red-striped 

 and sweet. A sharp line of division separates the two portions. Such fruits are borne on a tree pro- 

 duced by grafting one variety on another, the tree-trunk having grown from a bud which arose just 

 where stock and scion join, and which included cells derived from both sources. But the two kinds 

 of cells and all their descendants have retained their original distinctness, as the composite fruits •ehow. 

 Hence, not only may the body and germ-cells be of unlike character (as Figs. 2-7 show), but even the 

 body may be composite and yet each part retain its original character. By grafting tadpoles, Harrison 

 has produced a frog which anteriorly was of one species and posteriorly of another. If such a frog 

 produced eggs, their character would depend upon which part of the body furnished the eggs. " Graft- 

 hybrids " between the tomato and black nightshade (Solanum nigrum) produced by Winkler and 

 studied by him and by Baur were found to produce as seedlings either pure tomato plants or pure 

 nightshade plants, depending on which species made up that part of the " chimera " from which the 

 germ-cells arise. 



plasm. Now Weismann maintained that the germ-cells, since 

 they are not descended from body-cells but only from the 

 fertilized egg-cell, have no way of transmitting body-modifi- 

 cations, i. e., acquired characters. The germ-cells are guests 

 in the body, but not members of the household. They feed 

 at the common table but have no share in the other activities 



