THE PAST EVOLUTION OF MAN 83 



ment are precisely proportioned to the length and 

 salience of the stages in the racial history. It con- 

 tents us that there are innumerable admitted facts 

 which consort with this theory, and which, to those 

 who deny it, are meaningless and bewildering, 1 

 besides defying the primary law of animal economy. 

 It is incomprehensible why a developing animal 

 should expend weeks or months in the formation of 

 a large structure — a process which entails the ex- 

 penditure of valuable energy — the said structure 

 ultimately disappearing or undergoing atrophy, and 

 at no time performing any function, unless we 

 regard the performance of this " useless " process as 

 enforced upon the individual in virtue of the fact 

 that in its ancestors this structure was both perma- 

 nent and useful. The human tail is a case in point. 



Hence, whilst some decry the embryological 

 argument as overrated, we may nevertheless con- 

 sider the results of the extensive studies which 

 have recently been directed to embryology in 

 general and simian embryology in particular. 2 



It is found, as we have already seen, that the 

 mere external correspondence between the embryo 

 of man and of the anthropoid is extremely close. 

 This correspondence is seen, on dissection, to obtain 

 even in the more intimate details of internal de- 

 velopment. But of great significance is the fact 



1 For the best consideration in English of the recapitulation 

 theory, the reader should consult Mr. Archdall Eeid's recently 

 published "Principles of Heredity" (Chapman & Hall). 



2 For details the reader should refer to Haeckel's book already 

 mentioned. The veteran zoologist of Jena is the chief living ex- 

 ponent of the relations of embryology to evolutionary theory. See 

 Metchnikoff's " Nature of Man." 



