174 Darwin and Embryology 
greater rapidity at the beginning of life than in its later periods. As 
each of these stages is equal in value, for our present purpose, to the 
adult phase, it clearly follows that if there is anything in the view 
that the anatomical study of organisms is of importance in deter- 
mining their mutual relations, the study of the organism in its 
various embryonic (and larval) stages must have a greater importance 
than the study of the single and arbitrarily selected stage of life called 
the adult. 
But a deeper reason than this has been assigned for the im- 
portance of embryology in classification. It has been asserted, and is 
implied by Darwin in the passage quoted, that the ancestral history ig 
repeated in a condensed form in the embryonic, and that a study of 
the latter enables us to form a picture of the stages of structure 
through which the organism has passed in its evolution. It enables 
us on this view to reconstruct the pedigrees of animals and so to 
form a genealogical tree which shall be the true expression of their 
natural relations. 
The real question which we have to consider is to what extent the 
embryological studies of the last 50 years have confirmed or rendered 
probable this “theory of recapitulation.” In the first place it must 
be noted that the recapitulation theory is itself a deduction from 
the theory of evolution. The facts of embryology, particularly of 
vertebrate embryology, and of larval history receive, it is argued, an 
explanation on the view that-the successive stages of development 
are, on the whole, records of adult stages of structure which the 
species has passed through in its evolution. Whether this statement 
will bear a critical verbal examination I will not now pause to inquire, 
for it is more important to determine whether any independent facts 
can be alleged in favour of the theory. If it could be shown, as was 
stated to be the case by L. Agassiz, that ancient and extinct forms of 
life present features of structure now only found in embryos, we should 
have a body of facts of the greatest importance in the present 
discussion. But as Huxley! has shown and as the whole course of 
palaeontological and embryological investigation has demonstrated, 
no such statement can be made. The extinct forms of life are very 
similar to those now existing and there is nothing specially embryonic 
about them. So that the facts, as we know them, lend no support to 
theory. 
But there is another class of facts which have been alleged in 
favour of the theory, viz. the facts which have been included in the 
1 See Huxley’s Scientific Memoirs, London, 1898, Vol. «. p. 303: “There is no real 
parallel between the successive forms assumed in the development of the life of the 
individual at present, and those which have appeared at different epochs in the past.” 
See also his Address to the Geological Society of London (1862) ‘On the Palaeontological 
Evidence of Evolution,’ ibid. Vol. m. p. 512. 
