THE BIOGENETIC LAW 175 



said — ontogeny is nothing but a recapitulation of the phylogeny, 

 only with innumerable subtractions and interpolations, additions and 

 displacements of the organ-stages both in time and place. It would 

 be a great mistake to conclude from the fact of these manifold 

 alterations that the whole proposition of the recapitulation of the 

 phylogeny in the ontogeny is erroneous, or at least valueless. If its 

 only use were to enable us to read the racial history of a species out 

 of its germinal history, it is intelligible enough that we might be led 

 to give it up in despair, but I think that the main thing is to get 

 some insight into the history of the ontogeny, and there can be no 

 doubt that this can have been built up on no other foundation than 

 upon the racial history. What is new could only have arisen from 

 what was already in existence, and everything in ontogen}^, not only 

 the palingenetic stages which still represent in some measure the 

 facies of fully-formed ancestral stages, but also the ccenogenetic 

 stages, like the pupa-stage we have already discussed, have arisen 

 historically, nothing de novo, but all in connexion with what was 

 already present. But what was first present was in all cases the 

 stages of the ancestral forms. 



It is undoubtedly of the greatest value to be able to penetrate 

 more and more deeply into embryonic development, and to discover 

 more precisely the changes that have taken place throughout its 

 course in the originally existing material of ancestral forms. But 

 it must not be forgotten that, all transformations notwithstanding, 

 so much of the racial history is still very plainly indicated in the 

 germinal history, that this must always remain for us a most important 

 source from which to draw conclusions in regard to the phyletic 

 development of any animal group, I admit that these conclusions 

 have sometimes been drawn with too great confidence, but even if we 

 cannot regard as well founded Haeckel's view that in the ontosrenv 

 of Man there are fourteen different ancestral staofes recosfnizable, 

 a protist stage, a gastrsea stage, a prochordate, an acranial, a cyclo- 

 stome, a fish-stage, and so on, we must recognize that the unicellular 

 stage of ontogeny, with which even now the development of every 

 human being begins, undoubtedly repeats the facies of an ancestor, 

 although greatly altered ; for we must be descended from unicellular 

 organisms. The essential part of this ancestral stage is thus pre- 

 served in the ontogeny, and only what is special and in some measure 

 due to chance, that is, to adaptation to special conditions of existence, 

 has been modified. 



It has been supposed that the proposition that phylogeny is 

 recapitulated in the ontogeny is disproved, because the ontogenetic 



