The Recapitulation Theory in Biology 17 



outlines one may still hold with justice for the truth of this 

 threefold parallelism. 20 Its recurrence with Haeckel was con- 

 sequently the obvious thing on the part of one who desired to 

 present a panoramic view of the natural world after the manner 

 of Humboldt and Agassiz. The imperfections of the parallel- 

 ism would naturally appear subsequent to its original formula- 

 tion. 



It may have been the prestige of this parallelism in his mind, 

 together with the fact that he was for the time primarily a 

 morphologist, as the title of his book implies, that led Haeckel 

 to over-simplify the effects of heredity and adaptation through- 

 out descent, and to neglect somewhat the question of what was 

 required of these two factors to substantially support the paral- 

 lelism. This had been a matter of primary concern to Darwin 

 and Miiller, as has been noted. Throughout his works the 

 ontogenetic-phylogenetic parallelism is associated especially 

 with the "laws" of hereditary transmission at correspond- 

 ing ages and in corresponding place relations, and with that of 

 abbreviated heredity suggested by Miiller. 21 The effect of 

 the first two was to repeat the parental order; the effect of the 

 last was to simplify and shorten this order perhaps, but not to 

 destroy it. This is essentially the situation in the fifth edition 

 of the "Evolution of Man/' 22 where the symbolic representation 

 of the two series indicates omission of ancestral stages, and some 

 modification of them in ontogeny without obscuring their 

 identity. 



The appearance of novelty, or variation, was identified by 

 Haeckel with adaptation, or the direct modifying effect of 

 environment. This again would explain in part his over-em- 

 phasis of the conservative influence of heredity, for the ever- 

 recurring changes induced by germinal variations regardless 



" " It is indisputable, if we only consider the most general features, that the history 

 of the development of an individual is a kind of rapid recapitulation of the slow phases 

 of the evolution of the species and of the branch." Depgret, Transformations of the 

 Animal World, trans. 1909, p. 254. 



Jl "Der Parallelismus zwischen der phyletischen (palaontologischen) und der bion- 

 tischen (individuellen) Entwickelung erklart sich einfach mechanisch aus den Verer- 

 bungs-Gesetzen und insbesondere aus den Gesetzen der gleichzeitlichen, der gleichort- 

 lichen und der abgekurtzen Vererbung. Alle Erscheinungen, welche die individuelle 

 Entwiekelung begleiten, erklaren sich lediglich, soweit sie nicht unmittlebares Resultat 

 der Anpassung an neue Existenz-Bedingungen sind, aus der palaontologischen 

 Entwickelung der Vorfahren des Individuums. " Gen. Morph. II, p. 372. 



* 2 Trans., 1910, p. 4. 



