34 The Recapitulation Theory and Human Infancy 



that followed by other members of the group .... Again, it is 

 entirely arbitrary to assume that the group-characters are the 

 first to appear, and then successively those of the order, family, 

 genus, species. Finally .... we do not find early embryos of a 

 group identical, for with a sufficient knowledge of the develop- 

 ment it is always possible to distinguish between the embryos 

 of different species, as well as between adults, only it is more 

 difficult to do so, because the embryonic forms are simpler." 53 



In a study made in 1894 Sedgwick put the law to test by 

 making comparisons between embryos of closely allied animals 

 and embryos of animals remotely related. The observed facts 

 did not substantiate the law. 54 Sedgwick's more recent state- 

 ment is as follows: 



"The law asserts that embryos of different species of animals 

 of the same group are more alike than the adults and that, the 

 younger the embryo, the greater are the resemblances. If this 

 law could be established it would undoubtedly be a strong argu- 

 ment in favor of the "recapitulation" explanation of the facts 

 of embryology. But its truth has been seriously disputed. If 

 it were true we should expect to find that the embryos of closely 

 similar species would be indistinguishable from one another, 

 but this is notoriously not the case. It is more difficult to meet the 

 assertion when it is made in the form given above, for here we 

 are dealing with matters of opinion. For instance, no one would 

 4eny that the embryo of a dogfish is different from the embryo 

 of a rabbit, but there is room for difference of opinion when it is 

 asserted that the difference is less than the difference between 

 an adult dogfish and an adult rabbit. It would be perfect!^ 

 true to say that the differences between the embryos concern 

 other organs more than do the differences between the adults, 

 but who is prepared to affirm that the presence of a cephalic 

 coelom and of cranial segments, of external gills, of six gill slits, 

 of the kidney tubes opening into the muscle-plate coelom, of an 

 enormous yolk-sack, of a neurenteric canal, and the absence of 

 any trace of an amnion, of an allantois, and of a primitive streak 

 are not morphological facts of as high an import as those implied 

 by the differences between the adults? The generalization 

 undoubtedly had its origin in the fact that there is what may be 

 called a family resemblance between embryos and larvae, but 

 this resemblance, which is by no means exact, is largely superfi- 

 cial and does not extend to anatomical detail." 55 



From these authoritative statements it appears that the 

 facts of embryonic resemblances fail to support recapitulation 



5i Morgan, loc. cit., pp. 74, 75. 



M Quart. Journ. of Micros. Sci. Vol. 36, N. S., 1894, pp. 35-52. 



66 Darwin and Modern Science, p. 175. 



