Hertwig 239 



during ontogeny one after another in the same order as 

 in phylogeny? How does each of the successive general 

 states of the idioplasm, identical for the entire organism, 

 exert upon each individual cell so many special actions, 

 which are not only quite different from one another but 

 also are the exact reverse of those which by their union 

 had produced this general state during phylogeny? 



But however that may be, it is not at all certain that 

 Hertwig accepts this heaping up. For, as we have said 

 above, if he seems in certain places inclined to accept it, 

 he appears in others to reject it absolutely. 



He seems to accept it for example when he approves 

 and adopts the following passage from Nageli : 



"The unfolding of the anlagen of the idioplasm fol- 

 lows faithfully the phylogenetic order. While the or- 

 ganism, developing in ontogeny, runs successively 

 through the stages through which its phylogenetic stem 

 has run, the idioplasmatic anlagen become developed in 

 just that order in which they came into existence." 



And this conception appears confirmed in the follow- 

 ing words of Hertwig: "On account of the progressive 

 multiplication of the cells, their combined action is con- 

 stantly producing new embryonic states in the same serial 

 order as that in which they appeared during phylogeny. 

 The individual cells are brought into new relations to one 

 another and to the external world, and through these 

 successive reciprocal relations the anlagen latent in the 

 cells become awakened." 184 



In other places on the contrary he seems to reject 

 completely this heaping up of a w r hole series of anlagen, 

 of which each should correspond to the phylogenetic state 



184 Oscar Hertwig: Die Zelle und die Gewebe. II. P. 251, 253. 



