1893- THE PROBLEM OF VARIATION. 287 



to the present, the hypothesis that the properties of the germ-plasm 

 are modified by changes effected in the adult organs by external 

 influences still holds the field. 



It must be conceded, even by his opponents, that Weismann has 

 done a very great service to biological science by insisting upon and 

 forcing upon the general attention the actual relations of the germ- 

 cells to the soma. We cannot now overlook the fact that germ- cells 

 are not descended from the modified and specialised cells of the soma, 

 nor canMre any longer use a hypothesis of the construction of the germ- 

 cells from gemmules emitted by the somatic cells. The germ-cells, 

 like the cells of a muscle or a gland are derived directly from the 

 ovum by a succession of multiplying cells forming the germ-track ; 

 but we have still to discover how the ontogenetic properties of these 

 germ-cells are modified. In the present state of knowledge it is a 

 more irresistible conclusion that changes produced in the soma ulti- 

 mately affect the germ-cells, than that variations in the latter are due 

 to variations of nutrition in some manner which no one has attempted 

 to describe. 



J. T. Cunningham. 



