44 The Recapitulation Theory and Human Infancy 



"Our doctrine is, that the species-cell, even as the adult, 

 many-celled representative of the species, has passed through 

 a progressive, and, indeed, in general a corresponding develop- 

 ment in the course of phylogeny. This view appears to stand 

 in contradiction to the biogenetic law .... We must drop the 

 expression ' repetition of the form of extinct forefathers', and 

 put in its place the repetition of forms which are necessary for 

 organic development, and lead from the simple to the complex. . . 

 The egg-cell of the present time, and its one-celled predecessor 

 in the phylogenetic history, the amoeba, are only comparable 

 in so far as they fall under the common definition of the cell, 

 but beyond this they are extraordinarily different from each 

 other .... Undoubtedly there exists in a certain sense a parallel 

 between the phylogenetic, and the ontogenetic, development .... 

 Ontogenetic studies give us therefore only greatly changed copies 

 of phylogenetic stages. The two correspond not according to 

 their actual contents but only as to their form. " 71 



This is the argument and conclusion of the embryologist, O. 

 Hertwig (1898). Hertwig's concluding idea that the embryo 

 repeats the ancestral stage in its form only does not commend 

 itself to Morgan as a model of clear thinking: "Can we be asked 

 to believe for instance that a young chick repeats the ancestral 

 adult fish form but not the contents of the fish?" 72 



Montgomery was so greatly impressed by these physiological 

 considerations that he was compelled to repudiate recapitula- 

 tion in toto. 



"... .a new racial character is not something, like dead 

 ballast, passively transported by the germ plasm; it is a 

 change in the living processes .... The egg of a Mammal is as 

 dissimilar from that of a Fish as their adult stages, no matter 

 whether the differences are as perceptible or not. This was the 

 idea of the great old-master von Baer; the egg is as much a 



bird as is the hen The earlier the ontogenetic stage the 



more the individual may seem to be like its simple ancestors; 

 but in reality it is just as unlike them in those earlier stages 

 as in its matured condition. For degree of difference must not 

 be adjudged in this case from visible differences alone, but rather 

 equally well from differences in growth energies and ultra-ob- 

 servational structural bases, which, though not perceptible, are 

 nevertheless just as clearly proven to exist. .. .Therefore we 

 can only conclude that the embryogeny does not furnish any 



71 Quoted by Morgan, Evolution and Adaptation, pp. 78, 79, 80, 82. 

 Ibid., p. 83. 



