32 The Recapitulation Theory and Human Infancy 



So much is this the case, now that we know the second and fourth 

 digits are for a time fairly well developed, we might speak of a 

 Hipparion stage in the ontogeny of the horse. To admit that 

 the horse, before assuming its own specific characters, makes, as 

 it were, a deflection towards the not very ancient form Hipparion, 

 is hardly going far enough to justify the assertion that the horse 

 during its development assumes, one after another, the charac- 

 ters of its ancestors, or, in other words, except in the most limit- 

 ed sense, 'climbs its own ancestral tree.'" 60 



DepeYet, in the book to which reference has already been made, 

 not only presents an authoritative appraisement of the embry- 

 ological method of determining phylogenies, from the viewpoint 

 of palaeontology, but gives also a convenient summary of the 

 amount of correspondence of ontogeny with phylogeny as 

 determined from this same viewpoint: 



"Has Palaeontology completely confirmed the conclusions 

 thus drawn from the embryology of existing beings? We may 

 approach this important question by two different methods. 

 The first method, which is the oldest and the one most generally 

 employed, consists in finding in geological strata forms which in 

 the adult state reproduce one of the transitory phases through 

 which the development of an existing animal passes. We give 

 to these fossil forms the name of Persistent Embryonic types. 

 Palaeontology is able to furnish us with a fairly large number of 

 examples of this. Thus the Fishes of the Primary epoch, such 

 as the scaly Ganoids, have a soft vertebral column in a state of 

 embryonic tissue or notocord, as in the existing Ganoids or Teleo- 

 steans .... In the same way the Palaeozoic Amphibians pass, as 

 regards the ossification of the vertebral column, through a series 

 of progressive phases. . . . These different phases are reproduced 

 in the development of our present Reptiles and Amphibians. In 

 recent and modern Ruminants the bones of the metacarpus and 

 of the metatarsus, separate in the embryo and the young animal, 

 become welded later in the adult into a cannon-bone caused by 

 the fusion of the two metapods. We know among the early 

 Ruminants genera ... .in which the metacarpal and the metatarsal 

 bones remain distinct in the adult state. 



"We may also quote a few persistent types among the Inverte- 

 brates 



"But it must be clearly stated that these examples of representa- 

 tion in fossil adult species of the embryonic, or more correctly, 

 of the youthful characteristics of existing animals, cannot be 



<o Ewart, Journ. Anal, and Phys., Vol. XXVIII, 1893-94, pp. 348-350. 



