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250 THE EVOLUTION THEORY 



fewer descendants wliieli might inherit its tendency to produce inferior 

 spenn-cells, nnd conversely. Thus it is not the sperm- cells of any one 

 individual which are selected according to their fitness, it is the 

 individuals themselves which compete with one another in the pro- 

 duction of germ-cells which shall fertilize best, that is, most certainly. 

 TIk" struggle is thus not intercellular, but a struggle between persons. 



The same is true of all cells differentiated for particular functions; 

 every new kind of glandular, muscular, or nerve cell, such as have 

 arisen a thousandfold in the course of phylogeny, can only have 

 resulted from a struggle between individuals which turned on the 

 possession of the best cells of a particular kind, not from a struggle 

 between the cells themselves, since these would gain no advantage 

 from serving the organism, as a whole, better than others of their 

 kind. In regard to the sex-cells we might admit, in addition to 

 personal selection, the possibility of an internal struggle between the 

 sperm-cells or egg-cells of the same individual, inasmuch as each of 

 these cells is the primordium of a new individual, and as those better 

 adapted for reproduction might transmit their better quality to these 

 new individuals. I wall not here enter into my reasons for regarding 

 this idea as erroneous, for in any case this interpretation would not 

 apply to any other kind of cells. If, for instance, it were a question 

 of the transformation of an ordinary mucus or salivary gland into 

 a poison gland, it would not matter in the least to the individual cell 

 whether it yielded a harmless or a poisonous secretion; but individuals 

 with many poisonous cells would have an advantage in the struggle 

 for existence. 



I agree so far with Plate when he refers the differentiation of the 

 tissues entirely to personal selection, but not in his further conclusion 

 that histonal selection does not exist. , The ground-plan of the 

 architectural structure of the organ depends upon personal selection, 

 but the realization of the plan in particular cases is not predetermined 

 down to the minutest details, but is regulated by histonal selection,/ 

 and is thus to a certain extent an adaptation to local conditions of 

 stimulus. The direction, strength, and size of every single bone lamella 

 is not predetermined from the germ, but only the occurrence and 

 nature of bone-cells and bone lamellas in general. The direction 

 and the strength which these bone lamellse may assume depends on 

 the local conditions of strain and pressure which affect the cell-mass, 

 as is shown very clearly by the spongiosa of an obliquely healed bone, 

 which we have already described. 



But let us now turn to the question which is here most important 

 for us : u'hether functional adaptations can he transmitted. We must 



