Le Dantec 273 



law of the repetition of phylogeny by ontogeny, as we 

 have already had occasion to remark in connection with 

 the similar hypotheses of Spencer, Hertwig and several 

 others. This requires, as we have seen, the conception 

 of the addition of a new substance to all those formerly 

 present. 



All variations of the organism are ascribed by 

 LeDantec, as we have already seen, to total or partial 

 destruction of some of the different plastic substances 

 (a), which make up the living substance, whereby their 

 quantitative proportions become changed; but never to 

 the formation of new plastic substances. Likewise dif- 

 ferent species would differ from one another in the 

 number and quality of the plastic substances (a). From 

 this it follows: i, that no further development can be 

 effected by any given living matter, if the number of 

 its substances has become very small, and thus an abso- 

 lute inalterability must be established as soon as this 

 number is reduced to one; 2, that the development of 

 the species can have been produced only by successive 

 total destructions of an always greater number of these 

 plastic substances; 3, that the further a species is devel- 

 oped, the smaller therefore must be the number of the 

 plastic substances which form its respective living matter. 

 One would thus arrive at the absurdity, that the simpler 

 the living substance is the more complex must be the 

 organisms formed from it. 



Finally LeDantec, like Spencer, Hertwig and the 

 others is unable to explain histological differentiation by 

 this supposed similarity of living substance in all parts 

 of the organism : 



"A muscular element differs entirely from a nervous 

 epithelial element, and these differences are manifested 



