112 THE LESSON OF EVOLUTION 



The continuity of the germ-plasm has been shewn 

 to be a fact in some animals ; but, as we have seen, 

 it breaks down in Nitella. For here the somato- 

 plasrn of the leaf gives rise to the reproductive cells. 

 And if the supposed essential difference between 

 somato-plasm and germ-plasm does not exist in 

 plants, continuity of the germ-plasm cannot have 

 in animals the importance attributed to it by Pro- 

 fessor Weismann. 



There is no evidence to show , nor reason for sup- 

 posing with Galton, that a struggle for existence 

 takes place among the organic units ; but Weis- 

 mann ',s hypothesis of germinal selection may indicate 

 a possible mode of the accumulation of a variation 

 after it has been selected. That is, it may give rise 

 to definite variation ; but it does not explain the origi- 

 nation of a new one ; for the determinants must be 

 there before one of them can be better nourished 

 than the others. Neither is there any connection 

 between being better nourished and being selected. 



Dr. Eoux's hypothesis of intra-selection does not 

 touch the question of heredity. It is an attempt to 

 explain Goethe's " law of compensation and 

 economy of growth," which has also been advocated 

 by Mr. Herbert Spencer. ' The hypothesis supposes 

 that one organ is starved and dwindles, so that 

 another, which is more useful to the animal or 

 plant, may be better developed. Mr. Spencer says*' 

 ; ' It is a general law of nutrition , that when there is 

 a deficiency of food, the non-essential organs suffer 

 more than the essential ones ; and the unlikeness 



^"Principles of Biology," 2nd ed., vol. 1, p. 328. 



