THE EVOLUTION OF THE MAMMALIA. 27 
due to ancestral inheritance. This assumption made the inter- 
pretation of embryological evidence and the sifting of the old from 
the new a matter for the individual judgment ; and, in the absence 
of any generally accepted canons of interpretation or standard of 
value, there has been little harmony of result. To use a concrete 
illustration : embryology fails to show that the horse and the 
sheep are descended from five-toed ancestors, and gives a quite 
false impression as to the manner in which the extremely complex 
molar teeth of the horse have arisen. 
Professor E. B. Wilson has stated the case forcibly and in terms 
that will compel assent from most impartial minds: "It must be 
evident to any candid observer not only that the embryological 
method is open to criticism, but that the whole fabric of morphol- 
ogy, as far as it rests upon embryological evidence, stands in 
urgent need of reconstruction. For twenty years embryological 
research has been largely dominated by the recapitulation theory ; 
and unquestionably this theory has illuminated many dark places, 
and has solved many a perplexing problem that without its aid 
might have remained a standing riddle to the pure anatomist. 
But, while fully recognizing the real and substantial fruits of that 
theory, we should not close our eyes to the undeniable fact that 
it, like many another fruitful theory, has been pushed beyond its 
legitimate limits. It is largely to an overweening confidence in 
the value of the embryological evidence that we owe the vast 
number of the elaborate hypothetical phylogenies, which confront 
the modern student in such bewildering confusion. The inquiries 
of such a student regarding the origin of any of the great pri- 
mary types of animals, involve him in a labyrinth of speculation 
and hypothesis, in which he seeks in vain for conclusions of even 
approximate certainty." 1 
To recur to the comparison with the science of language, 
embryology resembles dealing with an ancient literature which 
has been preserved only in abstracts and abbreviations, and 
has been vitiated by many changes and forgeries, only the 
(1) Wood's Holl Biological Lectures, 1895, p. 103. 
