198 DARWINISM TO-DAY. 



next generation strong and extra-vigorous daughter deter- 

 minants. For any determinant in the germ-plasm of a fer- 

 tilised egg-cell has not alone to furnish determinants which 

 shall control the development of body-tissues and organs 

 of the individual which develops from this cell, but also to 

 furnish daughter determinants for the new germ-plasm of 

 this individual. This will result in a repetition of the 

 extra-development in the next generation of the same organs 

 as were strongly developed in the first generation, and the 

 under-development of the same organs as were weak or 

 wanting in the first generation. Which process continued 

 is simply determinate variation, that is, variation along 

 fixed lines without reference to personal selec- 

 lectioTresnlts" ^ on - Now when this variation becomes so 



indeterminate marked that it is of life-and-death advantage 

 or disadvantage in the life of the individual, it 

 will immediately become subject to the control of personal 

 natural selection, and under the influence of this dominant 

 factor in determining adaptation, either be further fostered 

 and fixed or be extinguished. If the increasing organ or 

 part due to germinal selection be one whose increase is 

 advantageous to the individuals possessing it, then natural 

 selection will preserve those individuals and the germinal 

 advantage of the determinants of this part will be steadily 

 increased, as the size and power of assimilation of the 

 determinants correspond to the size and vigour of the part. 

 By this theory Weismann believes that he has explained 

 away one of the most potent objections to natural selection, 

 viz., that it is necessary to assume, for the effective work of 

 selection, the timely appearance of the proper variations 

 necessary for the continued advantageous modification of 

 a part. "'Knowing this factor, we remove, it seems to me," 

 writes Weismann, 8 "the patent contradiction of the assump- 

 tion that the general fitness of organisms or the adaptations 

 necessary to their existence, are produced by accidental 



